feat(invoices): per-line percentage discount and separate fakturamarkning (#2084)

* feat(invoices): per-line percentage discount and separate fakturamarkning User request: rabatt i procent per artikelrad, and a marking field separate from Er referens. - invoice_items.discount_percent (0-100, default 0): line_total and vat_amount are stored NET of the discount. Shared exact-ore math in lib/invoices/line-amounts.ts (gross, discount, net) used by the web builder, staged-operation commit, editor preview, PDF, and Peppol. Undiscounted lines keep the legacy unrounded qty*price byte-identical. - ROT/RUT deduction computes on the discounted net line total. - invoices.invoice_marking: printed on the PDF next to the references and mapped to Peppol BT-10 BuyerReference (marking wins over your_reference; either satisfies the BT-10 requirement). - Peppol renders the discount as a BG-27 line AllowanceCharge (reason code 95, MultiplierFactorNumeric, Amount, BaseAmount). - Editor: "Lagg till rabatt" in the row menu (same reveal pattern as ROT/RUT), Markning row next to Er referens, forval chip, review dialog shows discounts and marking. - Plumbed through v1 REST projections, MCP create/get/update invoice tools, pending-operations update path, and copy-invoice (discount copied; marking deliberately not, it is recipient-specific). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01JJAt9yM7tgZ69f1XnNnq52 * fix(invoices): carry discount_percent through every deduction, credit, convert and preview path Skeptic + CI findings on the discount/marking feature, one pass: - generateRotRutLines and propose-send-lines now pass discount_percent into computeDeduction: the send/credit/cash verifikat booked 1513 on the GROSS line while deduction_total, the PDF and the Skatteverket claim carried the net, stranding the difference on 1513 and pushing 1510 negative once the customer paid. Test pins 1513=3000/1510=7000 for a 20%-discounted 10 000 kr ROT line. - preview-pdf route accepts discount_percent (net totals + net-based deduction) and invoice_marking; the editor now sends the marking, so the preview equals the invoice it becomes. - Credit notes carry discount_percent (buildCreditNoteItem, v1 credit route select+insert, MCP credit executor) and invoice_marking, so the kreditfaktura face arithmetic multiplies out and shows the Rabatt column (ML 17 kap 24 §). - Proforma->invoice convert copies discount_percent + invoice_marking: the converted invoice previously failed Peppol LINE_TOTAL_MISMATCH and lost the rebate on the next builder pass. - Editor hides the discount menu in self-billed mode (the self-billed wire shape has no discount; previewed net would book gross). - MCP staging and commitCreateInvoice reject a non-number discount_percent (a string coerced past the range check but was ignored by the totals math and still stored). - Regenerated skills/accounted-api (apiskill:check CI failure). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01JJAt9yM7tgZ69f1XnNnq52 --------- Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
2026-08-31 15:34:06 +02:00
parent 84c8e1ce59
commit f216a60bf8
35 changed files with 826 additions and 51 deletions
@@ -1384,6 +1384,7 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-31] Login/register methods come from GoTrue (/auth/v1/settings + admin customProviders) instead of app-side flags; NEXT_PUBLIC_GOOGLE_AUTH_ENABLED removed (PR #1869): the Supabase dashboard becomes the single switch, an allowlist of auth-js provider ids filters non-login entries like anonymous_users, and hosted rendering is unchanged because Google is enabled in prod GoTrue. The Vercel env var stays set for old-build rollback safety; delete it after a few deploys.
 [2026-08-31] Single prominent amount is PROMOTED into editable totals.total (totalSource='prominent') instead of living in a read-only Belopp row: Emil's call, an uncorrectable load-bearing value violated the prefill-override-editors rule. Provenance keeps matching fallback-grade (discount, date guard, hunt exclusion); a user edit of TOTALT clears the stamp. Multi-amount docs keep the Belopp row: promoting one of several figures would invent a total.
 [2026-08-31] Image-scan red fixed by bumping the node:22-alpine digest (alpine 3.23 to 3.24.1), not by widening the gate: the Dockerfile's apk-upgrade layer is frozen by the GHCR buildx layer cache, so a fix published after the last cache-busting change (libssl3 3.5.8-r0 for CVE-2026-14456) never reaches the published image until the FROM digest moves; the red scheduled scan is the designed alarm for exactly this bump. cron.Dockerfile gained the same apk upgrade (it had none).
+[2026-08-31] Per-line discount stores NET line_total via computeLineNet (roundOre(gross) minus roundOre(gross*d/100)) rather than round(gross*(1-d/100)): the subtracted-rounded-discount form keeps gross = discount + net exact in ore arithmetic, which the Peppol BG-27 line allowance (Amount + LineExtensionAmount = BaseAmount) and the PDF discount column both need; undiscounted lines keep the legacy unrounded qty*price so existing invoices and the Peppol LINE_TOTAL check stay byte-identical. ROT/RUT deducts on the discounted net (the customer pays that). invoice_marking is deliberately NOT copied by copy-invoice (recipient/PO-specific, same rule as your_reference) and NOT added to recurring schedules (follow-up if requested).
 [2026-08-31] Own-company-as-supplier guard nulls the supplier block instead of flagging or substituting the issuer: an empty LEVERANTOR is always safe, a guessed issuer is not; BYO/agent-supplied extraction paths are deliberately exempt (explicit input, not a model misread).
 [2026-08-31] gnubok-home-ok cache cookie is user-scoped (userId~host) instead of cleared on sign-out: sign-out happens client-side via supabase.auth.signOut so no server surface reliably sees it, while a value bound to the session's user makes any inherited verdict miss the cache by construction. Separator ~ because it is unreserved under encodeURIComponent AND a legal raw cookie octet, so the value round-trips identically whether or not the cookie layer percent-encodes. Old host-only cookies never match and self-heal; found via the amnas account-switch repro (two logins 9 s apart shared the verdict).
 [2026-08-31] Bookkeeping digest email is per-user per-COMPANY per-day (not one aggregated mail across companies): notification_log.company_id anchors the claim, subject lines stay unambiguous, and most users have one company; consultants can opt in and get one short mail per client. Window is a fixed last-24h (cron cadence) rather than tracking last-sent state. Settings toggle stays hardcoded Swedish like the rest of the push-notifications extension UI (no next-intl wiring in extension components); revisit if that surface is ever translated.
@@ -79,6 +79,8 @@ export const POST = withRouteContext<{ params: Promise<{ id: string }> }>(
      reverse_charge_text: proforma.reverse_charge_text,
      your_reference: proforma.your_reference,
      our_reference: proforma.our_reference,
+      // Buyer routing survives conversion (Peppol BT-10 may rely on it alone).
+      invoice_marking: proforma.invoice_marking ?? null,
      notes: proforma.notes,
      document_type: 'invoice',
      converted_from_id: id,
@@ -92,7 +94,7 @@ export const POST = withRouteContext<{ params: Promise<{ id: string }> }>(
    return NextResponse.json({ error: getUserErrorMessage(invoiceError) }, { status: 500 })
  }

-  const items = (proforma.items || []).map((item: { sort_order: number; line_type?: 'product' | 'text'; description: string; quantity: number; unit: string; unit_price: number; line_total: number; dimensions?: Record<string, string> }) => ({
+  const items = (proforma.items || []).map((item: { sort_order: number; line_type?: 'product' | 'text'; description: string; quantity: number; unit: string; unit_price: number; discount_percent?: number | null; line_total: number; dimensions?: Record<string, string> }) => ({
    invoice_id: invoice.id,
    sort_order: item.sort_order,
    line_type: item.line_type ?? 'product',
@@ -100,6 +102,10 @@ export const POST = withRouteContext<{ params: Promise<{ id: string }> }>(
    quantity: item.quantity,
    unit: item.unit,
    unit_price: item.unit_price,
+    // The stored line_total is net of this; dropping it would make the
+    // converted invoice fail the Peppol line check and lose the rebate on
+    // the next builder pass.
+    discount_percent: item.discount_percent ?? 0,
    line_total: item.line_total,
    dimensions: item.dimensions ?? {},
  }))
@@ -9,6 +9,8 @@ import { contentDisposition } from '@/lib/api/content-disposition'
 import type { InvoiceItem, Customer, CompanySettings, InvoiceDocumentType } from '@/types'
 import { errorResponseFromCode } from '@/lib/errors/get-structured-error'
 import { computeDeduction, computeInvoiceDeductionTotal, type DeductionType } from '@/lib/invoices/rot-rut-rules'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
+import { roundOre } from '@/lib/money'
 import { expandPersonnummerTo12, maskPersonnummer, validatePersonnummer } from '@/lib/salary/personnummer'
 import { revealStoredCustomerPersonalNumber } from '@/lib/customers/protect-personal-number'
 import {
@@ -29,6 +31,8 @@ interface PreviewItemInput {
  quantity: number
  unit: string
  unit_price: number
+  /** Line discount 0-100; amounts render net of it (line-amounts.ts). */
+  discount_percent?: number | null
  vat_rate?: number
  deduction_type?: DeductionType | null
  labor_hours?: number | null
@@ -83,7 +87,8 @@ export const POST = withRouteContext('invoice.preview_pdf', async (request, {
 }) => {
  const body = await request.json()
  const {
-    customer_id, invoice_date, due_date, delivery_date, currency, items, your_reference, our_reference, notes,
+    customer_id, invoice_date, due_date, delivery_date, currency, items, your_reference, our_reference,
+    invoice_marking, notes,
    document_type, invoice_number, payment_link_url,
    deduction_personnummer, deduction_housing_designation, deduction_apartment_number, deduction_brf_org_number,
  } = body
@@ -227,15 +232,19 @@ export const POST = withRouteContext('invoice.preview_pdf', async (request, {
  // deduction, mirroring build-invoice-write.ts so the preview states the
  // same avdrag row, info box and "Att betala" as the invoice it becomes.
  const invoiceItems: InvoiceItem[] = items.map((item: PreviewItemInput, index: number) => {
-    const lineTotal = Math.round(item.quantity * item.unit_price * 100) / 100
+    // Net of any per-line discount, same math as build-invoice-write.ts, so
+    // the preview totals equal the invoice the form creates.
+    const discountPercent = item.discount_percent ?? 0
+    const lineTotal = roundOre(computeLineNet(item.quantity, item.unit_price, discountPercent))
    const rate = zeroVat ? 0 : (item.vat_rate ?? vatRules.rate)
    const deductionType = deductionsApply ? (item.deduction_type ?? null) : null
-    // Same base as the write path: the line total inkl. moms at the rate the
-    // line is rendered with (HUSFL 6-9 §§).
+    // Same base as the write path: the NET line total inkl. moms at the rate
+    // the line is rendered with (HUSFL 6-9 §§).
    const deductionAmount = deductionType
      ? computeDeduction({
          unit_price: item.unit_price,
          quantity: item.quantity,
+          discount_percent: discountPercent,
          deduction_type: deductionType,
          vat_rate: rate,
        })
@@ -248,6 +257,7 @@ export const POST = withRouteContext('invoice.preview_pdf', async (request, {
      quantity: item.quantity,
      unit: item.unit,
      unit_price: item.unit_price,
+      discount_percent: discountPercent,
      line_total: lineTotal,
      vat_rate: rate,
      vat_amount: isDeliveryNote ? 0 : Math.round(lineTotal * (rate / 100) * 100) / 100,
@@ -275,6 +285,7 @@ export const POST = withRouteContext('invoice.preview_pdf', async (request, {
        invoiceItems.map((item) => ({
          unit_price: item.unit_price,
          quantity: item.quantity,
+          discount_percent: item.discount_percent ?? 0,
          deduction_type: item.deduction_type ?? null,
          vat_rate: item.vat_rate,
        })),
@@ -314,6 +325,7 @@ export const POST = withRouteContext('invoice.preview_pdf', async (request, {
    moms_ruta: vatRules.momsRuta,
    your_reference: your_reference || null,
    our_reference: our_reference || null,
+    invoice_marking: (typeof invoice_marking === 'string' && invoice_marking.trim()) || null,
    notes: notes || null,
    payment_link_url: previewPaymentLink,
    reverse_charge_text: vatRules.reverseChargeText || null,
@@ -392,6 +392,8 @@ async function createCreditNote(
      reverse_charge_text: originalInvoice.reverse_charge_text,
      your_reference: originalInvoice.your_reference,
      our_reference: originalInvoice.our_reference,
+      // Same buyer routing on the kreditfaktura as the original.
+      invoice_marking: originalInvoice.invoice_marking ?? null,
      // Positive magnitude, unlike the negated amounts above: the DB has
      // CHECK (deduction_total >= 0), and every reader either recomputes the
      // ROT/RUT amount from the items or skips credit notes entirely.
@@ -39,7 +39,7 @@ const CreditNoteRequest = z.object({
 })

 const ORIGINAL_INVOICE_COLUMNS =
-  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, currency, exchange_rate, exchange_rate_date, subtotal, subtotal_sek, vat_amount, vat_amount_sek, total, total_sek, vat_treatment, vat_rate, moms_ruta, your_reference, our_reference, notes, reverse_charge_text, credited_invoice_id, document_type, default_dimensions'
+  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, currency, exchange_rate, exchange_rate_date, subtotal, subtotal_sek, vat_amount, vat_amount_sek, total, total_sek, vat_treatment, vat_rate, moms_ruta, your_reference, our_reference, invoice_marking, notes, reverse_charge_text, credited_invoice_id, document_type, default_dimensions'

 // default_dimensions stays in this projection: the inserted credit-note row is
 // handed to createCreditNoteJournalEntry, which reads the bag off the row so
@@ -48,7 +48,7 @@ const CREDIT_NOTE_RESPONSE_COLUMNS =
  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, currency, exchange_rate, exchange_rate_date, subtotal, subtotal_sek, vat_amount, vat_amount_sek, total, total_sek, vat_treatment, vat_rate, moms_ruta, your_reference, our_reference, notes, reverse_charge_text, credited_invoice_id, document_type, paid_at, paid_amount, remaining_amount, default_dimensions, created_at, updated_at'

 const ORIGINAL_ITEMS_COLUMNS =
-  'sort_order, description, quantity, unit, unit_price, line_total, vat_rate, vat_amount, dimensions'
+  'sort_order, description, quantity, unit, unit_price, discount_percent, line_total, vat_rate, vat_amount, dimensions'

 const CreditNoteCreated = z.object({
  id: z.string().uuid(),
@@ -181,6 +181,7 @@ export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string
        quantity: number
        unit: string
        unit_price: number
+        discount_percent?: number | null
        line_total: number
        vat_rate?: number | null
        vat_amount?: number | null
@@ -246,6 +247,8 @@ export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string
      reverse_charge_text: original.reverse_charge_text ?? null,
      your_reference: original.your_reference ?? null,
      our_reference: original.our_reference ?? null,
+      // Same buyer routing on the kreditfaktura as the original.
+      invoice_marking: original.invoice_marking ?? null,
      notes: reason || `Krediterar faktura ${original.invoice_number ?? original.id}`,
      credited_invoice_id: originalId,
      status: 'sent' as const,
@@ -261,6 +264,9 @@ export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string
      quantity: -Math.abs(item.quantity),
      unit: item.unit,
      unit_price: item.unit_price,
+      // Carried so the kreditfaktura's face arithmetic multiplies out and the
+      // Rabatt column renders (ML 17 kap 24 §).
+      discount_percent: item.discount_percent ?? 0,
      line_total: -Math.abs(item.line_total),
      vat_rate: item.vat_rate ?? 0,
      vat_amount: -Math.abs(item.vat_amount ?? 0),
@@ -37,8 +37,9 @@ import {
 import { sortArticles } from '@/lib/articles/sort'
 import ArticleCombobox from '@/components/invoices/ArticleCombobox'
 import { getAmountToPay } from '@/lib/invoices/rounding'
+import { computeLineNet, hasLineDiscount } from '@/lib/invoices/line-amounts'
 import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogDescription, DialogFooter } from '@/components/ui/dialog'
-import { Loader2, X, ArrowLeft, Send, Eye, Landmark, Lock, AlertTriangle, MoreVertical, CalendarClock, Tags, Package, Copy } from 'lucide-react'
+import { Loader2, X, ArrowLeft, Send, Eye, Landmark, Lock, AlertTriangle, MoreVertical, CalendarClock, Tags, Package, Copy, Percent } from 'lucide-react'
 import {
  DropdownMenu,
  DropdownMenuTrigger,
@@ -259,6 +260,13 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
      quantity: z.number(),
      unit: z.string(),
      unit_price: z.number(),
+      // Rabatt i procent per rad (⋮ menu). null = no discount.
+      discount_percent: z
+        .number()
+        .min(0, t('validation_discount_range'))
+        .max(100, t('validation_discount_range'))
+        .nullable()
+        .optional(),
      vat_rate: z.number().min(0).max(25),
      // Article linkage (artikelregister). Optional: free-text lines omit them.
      article_id: z.string().nullable().optional(),
@@ -343,6 +351,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
      document_type: z.enum(['invoice', 'proforma', 'delivery_note']),
      your_reference: z.string().optional(),
      our_reference: z.string().optional(),
+      invoice_marking: z.string().optional(),
      notes: z.string().optional(),
      // Optional online payment link (pasted from e.g. the Stripe dashboard).
      // https-only: mirrors the server-side CreateInvoiceSchema gate.
@@ -453,6 +462,9 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
    [activeAccounts],
  )
  const [accountOverrideRows, setAccountOverrideRows] = useState<Set<number>>(new Set())
+  // Rabatt per rad: rows whose discount strip is open (⋮ menu), same
+  // lifecycle as the account override above. A stored discount also opens it.
+  const [discountRows, setDiscountRows] = useState<Set<number>>(new Set())
  // Dimension tagging (kostnadsställe/projekt, dimensions PR7). Affordances
  // render only when company_settings.dimensions_enabled: a UI-visibility
  // gate; a draft that already carries bags still round-trips untouched when
@@ -529,6 +541,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
          document_type: (initial.document_type ?? 'invoice') as InvoiceDocumentType,
          your_reference: initial.your_reference ?? '',
          our_reference: initial.our_reference ?? '',
+          invoice_marking: initial.invoice_marking ?? '',
          notes: initial.notes ?? '',
          payment_link_url: initial.payment_link_url ?? '',
          payment_link_auto: initial.payment_link_auto ?? true,
@@ -543,6 +556,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
            quantity: item.quantity,
            unit: item.unit,
            unit_price: item.unit_price,
+            discount_percent: hasLineDiscount(item.discount_percent) ? item.discount_percent : null,
            vat_rate: item.vat_rate ?? 25,
            article_id: item.article_id ?? null,
            revenue_account: item.revenue_account ?? null,
@@ -568,6 +582,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
            document_type: 'invoice' as InvoiceDocumentType,
            your_reference: '',
            our_reference: copyInitial.our_reference,
+            invoice_marking: '',
            notes: copyInitial.notes,
            payment_link_url: '',
            payment_link_auto: true,
@@ -635,6 +650,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
  const watchReceivedDate = watch('received_date')
  const watchDeliveryDate = watch('delivery_date')
  const watchYourReference = watch('your_reference')
+  const watchInvoiceMarking = watch('invoice_marking')
  const watchPaymentLinkUrl = watch('payment_link_url')
  const watchPaymentLinkAuto = watch('payment_link_auto')
  const watchPersonnummer = watch('deduction_personnummer')
@@ -817,6 +833,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
      quantity: 1,
      unit: 'st',
      unit_price: 0,
+      discount_percent: null,
      vat_rate: vatRegistered ? vatRatePlan.defaultRate : 0,
      article_id: null,
      revenue_account: null,
@@ -871,6 +888,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
      quantity: 0,
      unit: '',
      unit_price: 0,
+      discount_percent: null,
      vat_rate: 0,
      article_id: null,
      revenue_account: null,
@@ -1101,7 +1119,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
  }

  const subtotal = watchItems.reduce((sum, item) => {
-    return sum + (item.quantity || 0) * (item.unit_price || 0)
+    return sum + computeLineNet(item.quantity || 0, item.unit_price || 0, item.discount_percent)
  }, 0)

  const vatRules = selectedCustomer
@@ -1134,7 +1152,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
  let vatAmount = 0
  for (const item of watchItems) {
    const rate = vatRegistered ? (item.vat_rate ?? (vatRules?.rate || 25)) : 0
-    const lineTotal = (item.quantity || 0) * (item.unit_price || 0)
+    const lineTotal = computeLineNet(item.quantity || 0, item.unit_price || 0, item.discount_percent)
    const lineVat = Math.round(lineTotal * rate / 100 * 100) / 100
    vatAmount += lineVat
    const existing = vatByRate.get(rate) || { base: 0, vat: 0 }
@@ -1226,6 +1244,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
      const amount = computeDeduction({
        unit_price: item.unit_price || 0,
        quantity: item.quantity || 0,
+        discount_percent: item.discount_percent,
        deduction_type: item.deduction_type,
        // Same rate resolution as the VAT totals loop above: the deduction
        // base is the line total inkl. moms (HUSFL 6-9 §§).
@@ -1307,6 +1326,23 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
    }
  }

+  // Open/close the per-line discount (⋮ menu). Closing clears the value so
+  // the row books at full price again.
+  function toggleDiscount(index: number) {
+    const isOpen = discountRows.has(index) || hasLineDiscount(watchItems[index]?.discount_percent)
+    if (isOpen) {
+      setValue(`items.${index}.discount_percent`, null, { shouldDirty: true, shouldValidate: true })
+      setDiscountRows((prev) => {
+        const next = new Set(prev)
+        next.delete(index)
+        return next
+      })
+    } else {
+      setDiscountRows((prev) => new Set(prev).add(index))
+      window.setTimeout(() => setFocus(`items.${index}.discount_percent`), 0)
+    }
+  }
+
  // Open/close the optional per-item dimensions override (⋮ menu). Closing
  // clears the bag so the row falls back to the invoice's default_dimensions.
  function toggleItemDimensions(index: number) {
@@ -1754,6 +1790,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
          items: data.items,
          your_reference: data.your_reference,
          our_reference: data.our_reference,
+          invoice_marking: data.invoice_marking,
          notes: data.notes,
          payment_link_url: data.payment_link_url,
          invoice_number: numberPreview,
@@ -1882,6 +1919,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
    receivedDate: watchReceivedDate || '',
    deliveryDate: watchDeliveryDate || '',
    yourReference: watchYourReference || '',
+    invoiceMarking: watchInvoiceMarking || '',
    paymentLink: paymentLinkMode,
    oreRounding,
    dims: hasDimensionValues(defaultDims) ? compactDims(defaultDims) : null,
@@ -1904,6 +1942,8 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
        return t('chip_delivery', { date: chip.date })
      case 'your_reference':
        return t('chip_your_reference', { reference: chip.reference })
+      case 'invoice_marking':
+        return t('chip_invoice_marking', { marking: chip.marking })
      case 'payment_link':
        return chip.mode === 'auto' ? t('chip_stripe_auto') : t('chip_payment_link')
      case 'ore_off':
@@ -2156,7 +2196,11 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                        )
                      }

-                      const lineTotal = (item?.quantity || 0) * (item?.unit_price || 0)
+                      const lineTotal = computeLineNet(
+                        item?.quantity || 0,
+                        item?.unit_price || 0,
+                        item?.discount_percent,
+                      )
                      const rowErrors = errors.items?.[index]
                      const rowErrorMsg =
                        rowErrors?.description?.message ??
@@ -2166,6 +2210,12 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                      const articleStripOpen = articlePickerRows.has(index)
                      const accountStripOpen =
                        isInvoiceDoc && (accountOverrideRows.has(index) || Boolean(item?.revenue_account))
+                      // Not offered for a received självfaktura: the self-billed
+                      // endpoint's reduced item shape carries no discount, so a
+                      // previewed rebate would silently book gross.
+                      const discountStripOpen =
+                        !isSelfBilled &&
+                        (discountRows.has(index) || hasLineDiscount(item?.discount_percent))
                      const dimensionStripOpen =
                        dimensionsEnabled &&
                        isInvoiceDoc &&
@@ -2292,6 +2342,17 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                                      <Package className="h-4 w-4" />
                                      {t('row_menu_pick_article')}
                                    </DropdownMenuItem>
+                                    {!isSelfBilled && (
+                                      <>
+                                        <DropdownMenuSeparator />
+                                        <DropdownMenuItem onSelect={() => toggleDiscount(index)} className="py-2">
+                                          <Percent className="h-4 w-4" />
+                                          {discountStripOpen
+                                            ? t('row_menu_remove_discount')
+                                            : t('row_menu_add_discount')}
+                                        </DropdownMenuItem>
+                                      </>
+                                    )}
                                    {isInvoiceDoc && (
                                      <>
                                        <DropdownMenuSeparator />
@@ -2422,6 +2483,59 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                              </div>
                            )}

+                            {/* Rabatt strip: opened via the ⋮ menu; a stored
+                                discount keeps it open in edit mode. */}
+                            {discountStripOpen && (
+                              <div className="px-2 pb-3">
+                                <div className="flex flex-wrap items-center gap-2">
+                                  <Label
+                                    htmlFor={`invoice-line-discount-${index}`}
+                                    className="text-xs text-muted-foreground"
+                                  >
+                                    {t('discount_label')}
+                                  </Label>
+                                  <div className="flex items-center gap-1">
+                                    <Input
+                                      id={`invoice-line-discount-${index}`}
+                                      type="number"
+                                      step="0.01"
+                                      min={0}
+                                      max={100}
+                                      inputMode="decimal"
+                                      placeholder="0"
+                                      className="h-8 w-24 text-right tabular-nums"
+                                      aria-label={t('discount_label')}
+                                      aria-invalid={Boolean(rowErrors?.discount_percent) || undefined}
+                                      {...register(`items.${index}.discount_percent`, {
+                                        // valueAsNumber turns an emptied field into
+                                        // NaN, which the schema rejects invisibly;
+                                        // same pattern as labor_hours.
+                                        setValueAs: (v) => {
+                                          if (v === '' || v == null) return null
+                                          const n = Number(v)
+                                          return Number.isFinite(n) ? n : null
+                                        },
+                                      })}
+                                    />
+                                    <span className="text-xs text-muted-foreground">%</span>
+                                  </div>
+                                  {hasLineDiscount(item?.discount_percent) && (
+                                    <span className="text-xs tabular-nums text-muted-foreground">
+                                      &minus;{formatCurrency(
+                                        roundOre((item?.quantity || 0) * (item?.unit_price || 0)) - lineTotal,
+                                        watchCurrency,
+                                      )}
+                                    </span>
+                                  )}
+                                </div>
+                                {rowErrors?.discount_percent && (
+                                  <p className="mt-1 text-sm text-destructive">
+                                    {rowErrors.discount_percent.message}
+                                  </p>
+                                )}
+                              </div>
+                            )}
+
                            {/* ROT/RUT-avdrag strip: only when a deduction is
                                active on this row (chosen via the ⋮ menu). */}
                            {isInvoiceDoc && item?.deduction_type && (
@@ -2482,6 +2596,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                                    const amt = computeDeduction({
                                      unit_price: item?.unit_price || 0,
                                      quantity: item?.quantity || 0,
+                                      discount_percent: item?.discount_percent,
                                      deduction_type: item?.deduction_type,
                                      vat_rate: vatRegistered
                                        ? (item?.vat_rate ?? (vatRules?.rate || 25))
@@ -2924,6 +3039,23 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
                          />
                        </div>
                      </div>
+                      {/* Fakturamärkning: one buyer-required marking string
+                          (kostnadsställe/projekt/PO), separate from Er
+                          referens. Plain input, never comma-split. */}
+                      <div className={SETTINGS_ROW_CLASS}>
+                        <Label htmlFor="invoice_marking" className="text-[13px] font-normal">
+                          {t('invoice_marking_label')}
+                        </Label>
+                        <div className="w-56">
+                          <Input
+                            id="invoice_marking"
+                            maxLength={200}
+                            placeholder={t('invoice_marking_placeholder')}
+                            className="h-8 text-[13px]"
+                            {...register('invoice_marking')}
+                          />
+                        </div>
+                      </div>

                      {/* Online payment link: manual paste or the Stripe auto
                          toggle. Only real invoices; hidden unless the company
@@ -3212,6 +3344,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
            total={total}
            yourReference={pendingData?.your_reference}
            ourReference={pendingData?.our_reference}
+            invoiceMarking={pendingData?.invoice_marking}
            notes={pendingData?.notes}
            numberPreview={numberPreview}
            oreRounding={oreRounding}
@@ -7,6 +7,7 @@ import { Separator } from '@/components/ui/separator'
 import { formatCurrency, formatDate } from '@/lib/utils'
 import { getDisplayTotal } from '@/lib/invoices/rounding'
 import { isTextLikeLine } from '@/lib/invoices/display'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
 import { itemHasAccrual } from '@/lib/bookkeeping/accruals/account-suggestions'
 import type { Customer, Currency } from '@/types'

@@ -15,6 +16,8 @@ interface ReviewItem {
  quantity: number
  unit: string
  unit_price: number
+  /** Line discount 0-100; amounts render net of it. */
+  discount_percent?: number | null
  vat_rate?: number
  /** 'text' rows are free-text/blank lines: description only, no amounts. */
  line_type?: 'product' | 'text'
@@ -38,6 +41,7 @@ interface InvoiceReviewContentProps {
  total: number
  yourReference?: string
  ourReference?: string
+  invoiceMarking?: string
  notes?: string
  /** The invoice number that will be assigned on confirm. Null when unknown
   *  (e.g. delivery notes use a different sequence) or unfetched. */
@@ -63,6 +67,7 @@ export function InvoiceReviewContent({
  total,
  yourReference,
  ourReference,
+  invoiceMarking,
  notes,
  numberPreview,
  oreRounding,
@@ -84,7 +89,7 @@ export function InvoiceReviewContent({
  for (const item of items) {
    if (isTextLikeLine(item)) continue
    const rate = item.vat_rate ?? 0
-    const lineTotal = item.quantity * item.unit_price
+    const lineTotal = computeLineNet(item.quantity, item.unit_price, item.discount_percent)
    const lineVat = Math.round(lineTotal * rate / 100 * 100) / 100
    vatByRate.set(rate, (vatByRate.get(rate) || 0) + lineVat)
  }
@@ -182,12 +187,19 @@ export function InvoiceReviewContent({
                  </td>
                  <td className="py-2 text-right">{item.quantity}</td>
                  <td className="py-2 text-center">{item.unit}</td>
-                  <td className="py-2 text-right">{formatCurrency(item.unit_price, currency)}</td>
+                  <td className="py-2 text-right">
+                    {formatCurrency(item.unit_price, currency)}
+                    {(item.discount_percent ?? 0) > 0 && (
+                      <span className="ml-1 text-xs text-muted-foreground">
+                        &minus;{item.discount_percent}%
+                      </span>
+                    )}
+                  </td>
                  {showVatColumn && (
                    <td className="py-2 text-right">{item.vat_rate ?? 0}%</td>
                  )}
                  <td className="py-2 text-right">
-                    {formatCurrency(item.quantity * item.unit_price, currency)}
+                    {formatCurrency(computeLineNet(item.quantity, item.unit_price, item.discount_percent), currency)}
                  </td>
                </tr>
              )
@@ -214,11 +226,14 @@ export function InvoiceReviewContent({
                </p>
              )}
              <div className="flex items-center justify-between text-muted-foreground">
-                <span>{item.quantity} {item.unit} × {formatCurrency(item.unit_price, currency)}</span>
+                <span>
+                  {item.quantity} {item.unit} × {formatCurrency(item.unit_price, currency)}
+                  {(item.discount_percent ?? 0) > 0 && <> &minus;{item.discount_percent}%</>}
+                </span>
                {showVatColumn && <span className="text-xs">{t('mobile_vat_suffix', { rate: item.vat_rate ?? 0 })}</span>}
              </div>
              <p className="text-right font-medium">
-                {formatCurrency(item.quantity * item.unit_price, currency)}
+                {formatCurrency(computeLineNet(item.quantity, item.unit_price, item.discount_percent), currency)}
              </p>
            </div>
          )
@@ -260,7 +275,7 @@ export function InvoiceReviewContent({
      </div>

      {/* References/notes */}
-      {(yourReference || ourReference || notes) && (
+      {(yourReference || ourReference || invoiceMarking || notes) && (
        <div className="border-t pt-3 space-y-2 text-sm text-muted-foreground">
          {yourReference && (
            <p>
@@ -272,6 +287,11 @@ export function InvoiceReviewContent({
              <span>{t('our_reference')}</span> {ourReference}
            </p>
          )}
+          {invoiceMarking && (
+            <p>
+              <span>{t('invoice_marking')}</span> {invoiceMarking}
+            </p>
+          )}
          {notes && <p>{t('notes_prefix', { notes })}</p>}
        </div>
      )}
@@ -165,6 +165,7 @@ function chipsInput(overrides: Partial<ForvalChipsInput> = {}): ForvalChipsInput
    receivedDate: '',
    deliveryDate: '',
    yourReference: '',
+    invoiceMarking: '',
    paymentLink: null,
    oreRounding: true,
    dims: null,
@@ -221,6 +222,7 @@ describe('deriveForvalChips', () => {
        currency: 'EUR',
        deliveryDate: '2026-08-20',
        yourReference: 'Anna',
+        invoiceMarking: 'KST 4711',
        paymentLink: 'manual',
        oreRounding: false,
        dims: 'KS01 · P001',
@@ -230,6 +232,7 @@ describe('deriveForvalChips', () => {
    expect(chips).toContainEqual({ kind: 'currency', currency: 'EUR' })
    expect(chips).toContainEqual({ kind: 'delivery', date: '2026-08-20' })
    expect(chips).toContainEqual({ kind: 'your_reference', reference: 'Anna' })
+    expect(chips).toContainEqual({ kind: 'invoice_marking', marking: 'KST 4711' })
    expect(chips).toContainEqual({ kind: 'payment_link', mode: 'manual' })
    expect(chips).toContainEqual({ kind: 'dims', dims: 'KS01 · P001' })
    // ore_off is SEK-only: an EUR invoice has no öresavrundning to disable.
@@ -249,6 +252,7 @@ describe('deriveForvalChips', () => {
        receivedDate: '2026-08-15',
        documentType: 'proforma',
        yourReference: 'x',
+        invoiceMarking: 'x',
        paymentLink: 'auto',
        oreRounding: false,
        dims: 'KS01',
@@ -121,6 +121,7 @@ export type ForvalChip =
  | { kind: 'received'; date: string }
  | { kind: 'delivery'; date: string }
  | { kind: 'your_reference'; reference: string }
+  | { kind: 'invoice_marking'; marking: string }
  | { kind: 'payment_link'; mode: 'auto' | 'manual' }
  | { kind: 'ore_off' }
  | { kind: 'dims'; dims: string }
@@ -134,6 +135,7 @@ export interface ForvalChipsInput {
  receivedDate: string
  deliveryDate: string
  yourReference: string
+  invoiceMarking: string
  paymentLink: 'auto' | 'manual' | null
  oreRounding: boolean
  /** Compact display of the invoice-level default dims, or null when none. */
@@ -174,6 +176,9 @@ export function deriveForvalChips(input: ForvalChipsInput): ForvalChip[] {
  if (!input.isSelfBilled && input.yourReference.trim()) {
    chips.push({ kind: 'your_reference', reference: input.yourReference.trim() })
  }
+  if (!input.isSelfBilled && input.invoiceMarking.trim()) {
+    chips.push({ kind: 'invoice_marking', marking: input.invoiceMarking.trim() })
+  }
  if (!input.isSelfBilled && input.paymentLink) {
    chips.push({ kind: 'payment_link', mode: input.paymentLink })
  }
@@ -189,6 +189,7 @@ describe('gnubok_get_invoice: execute', () => {
      quantity: 2,
      unit: 'tim',
      unit_price: 1200,
+      discount_percent: 0,
      line_total: 2400,
      vat_rate: 25,
      vat_amount: 600,
@@ -359,6 +359,7 @@ describe('gnubok_update_invoice: validation and staging', () => {
    expect(result.preview.current_items).toEqual(
      CURRENT_ROWS.map((row) => ({
        ...row,
+        discount_percent: 0,
        deduction_type: null,
        accrual_period_start: null,
        accrual_period_end: null,
@@ -59,6 +59,7 @@ import { canApproveSupplierInvoice } from '@/lib/supplier-invoices/lifecycle'
 import { eventBus } from '@/lib/events/bus'
 import { getVatRules, getPermittedVatRates, getArticleVatRateAdoptionSet } from '@/lib/invoices/vat-rules'
 import { validateDeductionLines } from '@/lib/invoices/rot-rut-rules'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
 import { fetchExchangeRate, convertToSEK } from '@/lib/currency/riksbanken'
 import { getBranding } from '@/lib/branding/service'
 import { generateIncomeStatement } from '@/lib/reports/income-statement'
@@ -303,6 +304,8 @@ type StagedInvoiceLineInput = {
  quantity: number
  unit?: string
  unit_price?: number
+  /** Line discount 0-100 (rabatt i procent); totals are computed net of it. */
+  discount_percent?: number
  vat_rate?: number
  article_id?: string
  revenue_account?: string | null
@@ -370,10 +373,21 @@ function resolveInvoiceLineFromArticle(
      quantity: 0,
      unit: '',
      unit_price: 0,
+      discount_percent: 0,
      vat_rate: 0,
    }
  }
  if (!item.quantity || item.quantity <= 0) throw new Error(`Item ${lineNo}: quantity must be positive`)
+  // Strict typeof: a host that skips inputSchema validation could send a
+  // string, which JS comparisons would coerce past a bare range check while
+  // hasLineDiscount (typeof === 'number') then ignores it in the totals.
+  if (
+    item.discount_percent != null &&
+    (typeof item.discount_percent !== 'number' ||
+      !(item.discount_percent >= 0 && item.discount_percent <= 100))
+  ) {
+    throw new Error(`Item ${lineNo}: discount_percent must be a number between 0 and 100`)
+  }
  if (item.article_id && !article) {
    throw new Error(`Item ${lineNo}: article ${item.article_id} not found in this company. Use gnubok_list_articles to find valid IDs.`)
  }
@@ -6287,6 +6301,7 @@ export const tools: McpTool[] = [
        remaining_amount: { type: ['number', 'null'] },
        your_reference: { type: ['string', 'null'] },
        our_reference: { type: ['string', 'null'] },
+        invoice_marking: { type: ['string', 'null'], description: 'Fakturamärkning (buyer marking), separate from your_reference' },
        notes: { type: ['string', 'null'] },
        default_dimensions: { type: 'object', additionalProperties: { type: 'string' } },
        editable_draft: { type: 'boolean', description: 'true when gnubok_update_invoice can edit it' },
@@ -6303,6 +6318,7 @@ export const tools: McpTool[] = [
              quantity: { type: 'number' },
              unit: { type: 'string' },
              unit_price: { type: 'number' },
+              discount_percent: { type: 'number', description: 'Line discount 0-100; line_total is net of it' },
              line_total: { type: 'number' },
              vat_rate: { type: 'number' },
              vat_amount: { type: 'number' },
@@ -6345,7 +6361,7 @@ export const tools: McpTool[] = [
      const { data: invoice, error } = await supabase
        .from('invoices')
        .select(
-          'id, invoice_number, status, document_type, customer_id, invoice_date, due_date, delivery_date, currency, subtotal, vat_amount, total, paid_amount, remaining_amount, your_reference, our_reference, notes, default_dimensions, journal_entry_id, is_self_billed, credited_invoice_id, customer:customers(name), items:invoice_items(id, sort_order, line_type, description, quantity, unit, unit_price, line_total, vat_rate, vat_amount, article_id, revenue_account, deduction_type, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, accrual_period_start, accrual_period_end, accrual_balance_account, dimensions)',
+          'id, invoice_number, status, document_type, customer_id, invoice_date, due_date, delivery_date, currency, subtotal, vat_amount, total, paid_amount, remaining_amount, your_reference, our_reference, invoice_marking, notes, default_dimensions, journal_entry_id, is_self_billed, credited_invoice_id, customer:customers(name), items:invoice_items(id, sort_order, line_type, description, quantity, unit, unit_price, discount_percent, line_total, vat_rate, vat_amount, article_id, revenue_account, deduction_type, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, accrual_period_start, accrual_period_end, accrual_balance_account, dimensions)',
        )
        .eq('id', invoiceId)
        .eq('company_id', companyId)
@@ -6362,6 +6378,7 @@ export const tools: McpTool[] = [
        quantity: number
        unit: string
        unit_price: number
+        discount_percent: number | null
        line_total: number
        vat_rate: number
        vat_amount: number | null
@@ -6390,6 +6407,7 @@ export const tools: McpTool[] = [
        quantity: row.quantity,
        unit: row.unit,
        unit_price: row.unit_price,
+        discount_percent: row.discount_percent ?? 0,
        line_total: row.line_total,
        vat_rate: row.vat_rate,
        vat_amount: row.vat_amount ?? 0,
@@ -6427,6 +6445,7 @@ export const tools: McpTool[] = [
        remaining_amount: invoice.remaining_amount ?? null,
        your_reference: invoice.your_reference ?? null,
        our_reference: invoice.our_reference ?? null,
+        invoice_marking: invoice.invoice_marking ?? null,
        notes: invoice.notes ?? null,
        default_dimensions: (invoice.default_dimensions as Record<string, string> | null) ?? {},
        editable_draft: isEditableInvoiceDraft(invoice),
@@ -6456,6 +6475,7 @@ export const tools: McpTool[] = [
              quantity: { type: 'number' },
              unit: { type: 'string', description: 'st, tim, dag, mån' },
              unit_price: { type: 'number', description: 'Price per unit excl. VAT' },
+              discount_percent: { type: 'number', description: 'Line discount 0-100 (rabatt); line total and VAT computed net of it' },
              vat_rate: { type: 'number', description: 'VAT rate 0-100 (optional override)' },
              article_id: {
                type: 'string',
@@ -6483,6 +6503,7 @@ export const tools: McpTool[] = [
        currency: { type: 'string', enum: ['SEK', 'EUR', 'USD', 'GBP', 'NOK', 'DKK'] },
        our_reference: { type: 'string' },
        your_reference: { type: 'string' },
+        invoice_marking: { type: 'string', description: 'Fakturamärkning (buyer marking/PO label), separate from your_reference; feeds Peppol BuyerReference.' },
        notes: { type: 'string' },
        payment_link_url: {
          type: 'string',
@@ -6603,8 +6624,11 @@ export const tools: McpTool[] = [
      const permittedRates = getPermittedVatRates(customer.customer_type, customer.vat_number_validated)
      const allowedRates = new Set(permittedRates.map((r) => r.rate))

-      // Calculate per-item VAT
-      const subtotal = items.reduce((s, item) => s + item.quantity * item.unit_price, 0)
+      // Calculate per-item VAT (line totals net of any per-line discount)
+      const subtotal = items.reduce(
+        (s, item) => s + computeLineNet(item.quantity, item.unit_price, item.discount_percent),
+        0,
+      )
      let vatAmount = 0
      for (const item of items) {
        const itemRate = item.vat_rate !== undefined ? item.vat_rate : vatRules.rate
@@ -6614,7 +6638,7 @@ export const tools: McpTool[] = [
            `Allowed rates: ${permittedRates.map((r) => r.rate + '%').join(', ')}`
          )
        }
-        const lineTotal = item.quantity * item.unit_price
+        const lineTotal = computeLineNet(item.quantity, item.unit_price, item.discount_percent)
        vatAmount += Math.round(lineTotal * itemRate / 100 * 100) / 100
      }
      const total = subtotal + vatAmount
@@ -6641,6 +6665,7 @@ export const tools: McpTool[] = [
          currency,
          our_reference: (args.our_reference as string) || null,
          your_reference: (args.your_reference as string) || null,
+          invoice_marking: (args.invoice_marking as string) || null,
          notes: (args.notes as string) || null,
          payment_link_url: paymentLinkUrl,
        },
@@ -6649,7 +6674,7 @@ export const tools: McpTool[] = [
          customer_type: customer.customer_type,
          items: stagedItems.map(item => ({
            ...item,
-            line_total: item.quantity * item.unit_price,
+            line_total: computeLineNet(item.quantity, item.unit_price, item.discount_percent),
            vat_rate: item.vat_rate ?? vatRules.rate,
          })),
          subtotal: Math.round(subtotal * 100) / 100,
@@ -17174,6 +17199,7 @@ export const tools: McpTool[] = [
        delivery_date: { type: ['string', 'null'], description: 'YYYY-MM-DD; null clears the delivery date.' },
        your_reference: { type: 'string' },
        our_reference: { type: 'string' },
+        invoice_marking: { type: 'string', description: 'Fakturamärkning (buyer marking/PO label), separate from your_reference.' },
        items: {
          type: 'array',
          items: {
@@ -17183,6 +17209,7 @@ export const tools: McpTool[] = [
              quantity: { type: 'number' },
              unit: { type: 'string', description: 'st, tim, dag, mån' },
              unit_price: { type: 'number', description: 'Price per unit excl. VAT' },
+              discount_percent: { type: 'number', description: 'Line discount 0-100 (rabatt); pass back to keep it, totals computed net of it.' },
              vat_rate: { type: 'number', description: 'VAT rate 0-100 (optional override)' },
              article_id: {
                type: 'string',
@@ -17259,7 +17286,7 @@ export const tools: McpTool[] = [
      }

      const headerChanges: Record<string, unknown> = {}
-      for (const key of ['notes', 'invoice_date', 'due_date', 'delivery_date', 'your_reference', 'our_reference']) {
+      for (const key of ['notes', 'invoice_date', 'due_date', 'delivery_date', 'your_reference', 'our_reference', 'invoice_marking']) {
        if (args[key] !== undefined) headerChanges[key] = args[key]
      }
      if (rawItems === undefined && args.default_dimensions === undefined && Object.keys(headerChanges).length === 0) {
@@ -17364,7 +17391,7 @@ export const tools: McpTool[] = [
              `Allowed rates: ${permittedRates.map((r) => r.rate + '%').join(', ')}`
            )
          }
-          const lineTotal = item.quantity * item.unit_price
+          const lineTotal = computeLineNet(item.quantity, item.unit_price, item.discount_percent)
          subtotal += lineTotal
          vatAmount += roundOre(lineTotal * itemRate / 100)
        }
@@ -17379,6 +17406,7 @@ export const tools: McpTool[] = [
            deductionLines.map((item) => ({
              unit_price: item.unit_price,
              quantity: item.quantity,
+              discount_percent: item.discount_percent ?? 0,
              deduction_type: item.deduction_type ?? null,
              vat_rate: item.vat_rate ?? vatRules.rate,
              labor_hours: item.labor_hours ?? null,
@@ -17421,7 +17449,7 @@ export const tools: McpTool[] = [
        // the property columns are not needed for the preview.
        const { data: currentRows, error: currentError } = await supabase
          .from('invoice_items')
-          .select('line_type, description, quantity, unit, unit_price, line_total, vat_rate, revenue_account, article_id, deduction_type, accrual_period_start, accrual_period_end')
+          .select('line_type, description, quantity, unit, unit_price, discount_percent, line_total, vat_rate, revenue_account, article_id, deduction_type, accrual_period_start, accrual_period_end')
          .eq('invoice_id', invoice.id)
          .order('sort_order', { ascending: true })
        if (currentError) throw dbError(currentError)
@@ -17431,6 +17459,7 @@ export const tools: McpTool[] = [
          quantity: row.quantity,
          unit: row.unit,
          unit_price: row.unit_price,
+          discount_percent: row.discount_percent ?? 0,
          line_total: row.line_total,
          vat_rate: row.vat_rate,
          revenue_account: row.revenue_account ?? null,
@@ -14,6 +14,7 @@ import { DimensionsBagSchema } from '@/lib/bookkeeping/dimension-resolver'
 import { validateEmployeeBankAccount } from '@/lib/salary/payment/bank-account'
 import { MAX_INVOICE_EMAIL_COPY_RECIPIENTS } from '@/lib/invoices/email-recipients'
 import { INVOICE_POSTING_ACCOUNT_REGEX } from '@/lib/invoices/posting-account'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
 import {
  DEDUCTION_LINE_ERRORS,
  HOUSEWORK_TYPE_VALUES,
@@ -403,6 +404,10 @@ export const CreateInvoiceItemSchema = z
    quantity: z.number(),
    unit: z.string(),
    unit_price: z.number(),
+    // Percentage discount on the line (rabatt i procent per artikelrad).
+    // line_total and vat_amount are computed NET of this server-side
+    // (lib/invoices/line-amounts.ts); the client never sends a total.
+    discount_percent: z.number().min(0).max(100).nullable().optional(),
    vat_rate: z.number().min(0).max(100).optional(),
    // Article linkage. `article_id` ties the line to a catalog article (text
    // rows omit it). `revenue_account` is the legacy wire name for the optional
@@ -459,7 +464,8 @@ export const CreateInvoiceItemSchema = z
          message: 'ROT/RUT-rader kan inte periodiseras',
        })
      }
-      if (item.quantity * item.unit_price <= 0) {
+      // Net of any line discount: a 100 % rebated row has nothing to defer.
+      if (computeLineNet(item.quantity, item.unit_price, item.discount_percent) <= 0) {
        ctx.addIssue({
          code: z.ZodIssueCode.custom,
          path: ['accrual_period_start'],
@@ -520,6 +526,10 @@ const CreateInvoiceBaseSchema = z.object({
  document_type: InvoiceDocumentTypeSchema.optional(),
  your_reference: z.string().optional(),
  our_reference: z.string().optional(),
+  // Fakturamärkning: buyer-required marking (kostnadsställe/projekt/PO),
+  // separate from your_reference. Printed on the PDF and mapped to Peppol
+  // BT-10 BuyerReference when set.
+  invoice_marking: z.string().max(200).optional(),
  notes: z.string().optional(),
  // Optional online payment link (manual MVP): the user pastes a link created
  // in their PSP dashboard (e.g. a Stripe Payment Link). https-only because the
@@ -12,7 +12,7 @@
 */

 export const INVOICE_FULL_COLUMNS =
-  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, currency, exchange_rate, exchange_rate_date, subtotal, subtotal_sek, vat_amount, vat_amount_sek, total, total_sek, ore_rounding, vat_treatment, vat_rate, moms_ruta, your_reference, our_reference, notes, payment_link_url, stripe_payment_link_id, payment_link_auto, reverse_charge_text, credited_invoice_id, document_type, converted_from_id, paid_at, paid_amount, remaining_amount, default_dimensions, deduction_total, deduction_personnummer_last4, created_at, updated_at'
+  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, currency, exchange_rate, exchange_rate_date, subtotal, subtotal_sek, vat_amount, vat_amount_sek, total, total_sek, ore_rounding, vat_treatment, vat_rate, moms_ruta, your_reference, our_reference, invoice_marking, notes, payment_link_url, stripe_payment_link_id, payment_link_auto, reverse_charge_text, credited_invoice_id, document_type, converted_from_id, paid_at, paid_amount, remaining_amount, default_dimensions, deduction_total, deduction_personnummer_last4, created_at, updated_at'

 /**
 * Projection for the v1 PDF download route. Narrower than INVOICE_FULL_COLUMNS
@@ -31,8 +31,8 @@ export const INVOICE_FULL_COLUMNS =
 export const INVOICE_PDF_COLUMNS =
  'id, invoice_number, customer_id, invoice_date, due_date, delivery_date, status, document_type, ' +
  'currency, subtotal, vat_amount, total, ore_rounding, vat_treatment, vat_rate, moms_ruta, ' +
-  'reverse_charge_text, your_reference, our_reference, notes, credited_invoice_id, ' +
+  'reverse_charge_text, your_reference, our_reference, invoice_marking, notes, credited_invoice_id, ' +
  'paid_amount, remaining_amount, deduction_total, deduction_personnummer_last4'

 export const INVOICE_ITEM_FULL_COLUMNS =
-  'id, sort_order, line_type, description, quantity, unit, unit_price, line_total, vat_rate, vat_amount, article_id, revenue_account, deduction_type, deduction_amount, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, dimensions, created_at'
+  'id, sort_order, line_type, description, quantity, unit, unit_price, discount_percent, line_total, vat_rate, vat_amount, article_id, revenue_account, deduction_type, deduction_amount, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, dimensions, created_at'
@@ -1316,6 +1316,44 @@ describe('createInvoiceJournalEntry: ROT/RUT-avdrag', () => {
    expect(totalDebit).toBe(12500)
  })

+  it('discounted ROT line: 1513 books the NET-based deduction, matching the stored deduction_total', async () => {
+    // 10 000 kr labor, 20% rabatt → net 8 000 + 25% VAT 2 000 = 10 000.
+    // ROT = 30% of the NET inkl.-moms labor = 30% of 10 000 = 3 000, the same
+    // figure build-invoice-write stores on deduction_total and the payout
+    // request claims. Booking the gross (3 750) would strand 750 kr on 1513
+    // and push kundfordringar (1510) negative when the customer pays 7 000.
+    const invoice = makeInvoice({
+      subtotal: 8000,
+      vat_amount: 2000,
+      total: 10000,
+      vat_treatment: 'standard_25',
+      deduction_total: 3000,
+      items: [
+        makeItem({
+          quantity: 1,
+          unit_price: 10000,
+          discount_percent: 20,
+          line_total: 8000,
+          vat_rate: 25,
+          vat_amount: 2000,
+          deduction_type: 'rot',
+          deduction_amount: 3000,
+        }),
+      ],
+    })
+
+    await createInvoiceJournalEntry(null as never, 'company-1', 'user-1', invoice)
+
+    const input = mockedCreateEntry.mock.calls[0][3]
+    const debit1513 = input.lines.find((l) => l.account_number === '1513')
+    expect(debit1513?.debit_amount).toBe(3000)
+    const debit1510 = input.lines.find((l) => l.account_number === '1510')
+    expect(debit1510?.debit_amount).toBe(7000)
+    const totalDebit = input.lines.reduce((sum, l) => sum + l.debit_amount, 0)
+    const totalCredit = input.lines.reduce((sum, l) => sum + l.credit_amount, 0)
+    expect(totalDebit).toBe(totalCredit)
+  })
+
  it('mixed invoice: ROT line + non-deduction line, per-item handling', async () => {
    // ROT line 10 000 (deduction 30% of 12 500 inkl. moms = 3 750) +
    // non-deduction materials line 4 000.
@@ -331,6 +331,10 @@ function generateRotRutLines(
    const amount = computeDeduction({
      unit_price: side === 'credit' ? Math.abs(item.unit_price) : item.unit_price,
      quantity: side === 'credit' ? Math.abs(item.quantity) : item.quantity,
+      // The deduction base is the NET line total (rabatt reduces what the
+      // customer pays); omitting this books 1513 on the gross while the
+      // stored deduction_total and the Skatteverket claim carry the net.
+      discount_percent: item.discount_percent ?? 0,
      deduction_type: item.deduction_type,
      vat_rate: item.vat_rate,
    })
@@ -245,6 +245,9 @@ function buildSendLines(
    const deduction = computeDeduction({
      unit_price: item.unit_price,
      quantity: item.quantity,
+      // Net of any line discount: must match the stored deduction_total or
+      // the proposed 1513/1510 split cannot clear.
+      discount_percent: item.discount_percent ?? 0,
      deduction_type: item.deduction_type,
      vat_rate: item.vat_rate,
    })
@@ -52,4 +52,19 @@ describe('buildCreditNoteItem', () => {
      dimensions: { '6': 'P001' },
    })
  })
+
+  it('carries discount_percent so the kreditfaktura face arithmetic multiplies out', () => {
+    // Original: 2 x 1000 with 10% rabatt → net 1800. The credit row must keep
+    // the discount, or -2 x 1000 next to Summa -1800 prints with no visible
+    // prisnedsättning (ML 17 kap 24 §) and violates the stored net invariant.
+    const result = buildCreditNoteItem('credit-1', item({ discount_percent: 10, line_total: 1800, vat_amount: 450 }))
+    expect(result).toMatchObject({
+      quantity: -2,
+      discount_percent: 10,
+      line_total: -1800,
+      vat_amount: -450,
+    })
+    // Legacy rows without the column default to 0.
+    expect(buildCreditNoteItem('credit-1', item()).discount_percent).toBe(0)
+  })
 })
@@ -0,0 +1,173 @@
+import { describe, expect, it } from 'vitest'
+import type { SupabaseClient } from '@supabase/supabase-js'
+import { createQueuedMockSupabase, makeCustomer } from '@/tests/helpers'
+import { computeLineAmounts, computeLineNet, hasLineDiscount } from '@/lib/invoices/line-amounts'
+import { computeDeduction } from '@/lib/invoices/rot-rut-rules'
+import { buildInvoiceWriteData } from '@/lib/invoices/build-invoice-write'
+
+describe('computeLineAmounts', () => {
+  it('passes qty * price through untouched when no discount applies', () => {
+    // Legacy parity: existing invoices store the unrounded product.
+    expect(computeLineAmounts(3, 33.333)).toEqual({
+      gross: 3 * 33.333,
+      discount: 0,
+      net: 3 * 33.333,
+    })
+    expect(computeLineAmounts(2, 100, null)).toEqual({ gross: 200, discount: 0, net: 200 })
+    expect(computeLineAmounts(2, 100, 0)).toEqual({ gross: 200, discount: 0, net: 200 })
+  })
+
+  it('computes discount and net in exact ore arithmetic', () => {
+    expect(computeLineAmounts(2, 100, 10)).toEqual({ gross: 200, discount: 20, net: 180 })
+    // 1 * 99.99 at 33%: gross 99.99, discount round(32.9967) = 33.00, net 66.99.
+    expect(computeLineAmounts(1, 99.99, 33)).toEqual({ gross: 99.99, discount: 33, net: 66.99 })
+    // gross - discount is always exact: net + discount reconstructs gross.
+    const amounts = computeLineAmounts(7, 123.45, 12.5)
+    expect(amounts.net + amounts.discount).toBeCloseTo(amounts.gross, 10)
+  })
+
+  it('handles a 100% discount as a zero net line', () => {
+    expect(computeLineAmounts(4, 250, 100)).toEqual({ gross: 1000, discount: 1000, net: 0 })
+    expect(computeLineNet(4, 250, 100)).toBe(0)
+  })
+
+  it('hasLineDiscount treats null/undefined/0 as no discount', () => {
+    expect(hasLineDiscount(undefined)).toBe(false)
+    expect(hasLineDiscount(null)).toBe(false)
+    expect(hasLineDiscount(0)).toBe(false)
+    expect(hasLineDiscount(0.5)).toBe(true)
+  })
+})
+
+describe('computeDeduction with a line discount', () => {
+  it('deducts on the net line total (what the customer pays)', () => {
+    // 10 tim * 1000 = 10 000, 10% rabatt -> 9 000 net, incl VAT 11 250,
+    // ROT 30% = 3 375 (vs 3 750 undiscounted).
+    expect(
+      computeDeduction({
+        unit_price: 1000,
+        quantity: 10,
+        discount_percent: 10,
+        deduction_type: 'rot',
+        vat_rate: 25,
+      }),
+    ).toBe(3375)
+    expect(
+      computeDeduction({ unit_price: 1000, quantity: 10, deduction_type: 'rot', vat_rate: 25 }),
+    ).toBe(3750)
+  })
+})
+
+describe('buildInvoiceWriteData with per-line discount and invoice_marking', () => {
+  const baseHeader = {
+    customer_id: 'customer-1',
+    invoice_date: '2026-06-15',
+    due_date: '2026-07-15',
+    currency: 'SEK' as const,
+  }
+
+  it('stores net line totals, VAT on the net, and the discount on the row', async () => {
+    const { supabase, enqueue } = createQueuedMockSupabase()
+    enqueue({ data: { vat_registered: true }, error: null })
+
+    const customer = makeCustomer({ customer_type: 'swedish_business' })
+    const result = await buildInvoiceWriteData({
+      supabase: supabase as unknown as SupabaseClient,
+      companyId: 'company-1',
+      customer,
+      documentType: 'invoice',
+      input: {
+        ...baseHeader,
+        items: [
+          { description: 'Konsult', quantity: 10, unit: 'tim', unit_price: 1000, vat_rate: 25, discount_percent: 10 },
+          { description: 'Resa', quantity: 1, unit: 'st', unit_price: 500, vat_rate: 25 },
+        ],
+      },
+    })
+
+    expect(result.ok).toBe(true)
+    if (!result.ok) return
+    // 10 000 - 10% = 9 000 net + 500 undiscounted.
+    expect(result.invoiceFields.subtotal).toBe(9500)
+    expect(result.invoiceFields.vat_amount).toBe(2375)
+    expect(result.invoiceFields.total).toBe(11875)
+    expect(result.items[0]).toMatchObject({
+      discount_percent: 10,
+      line_total: 9000,
+      vat_amount: 2250,
+      unit_price: 1000,
+    })
+    expect(result.items[1]).toMatchObject({ discount_percent: 0, line_total: 500 })
+  })
+
+  it('maps invoice_marking to a concrete trimmed value, null when absent or blank', async () => {
+    const customer = makeCustomer({ customer_type: 'swedish_business' })
+    const items = [{ description: 'Konsult', quantity: 1, unit: 'tim', unit_price: 100, vat_rate: 25 }]
+
+    const { supabase, enqueue } = createQueuedMockSupabase()
+    enqueue({ data: { vat_registered: true }, error: null })
+    const withMarking = await buildInvoiceWriteData({
+      supabase: supabase as unknown as SupabaseClient,
+      companyId: 'company-1',
+      customer,
+      documentType: 'invoice',
+      input: { ...baseHeader, invoice_marking: '  KST 4711  ', items },
+    })
+    expect(withMarking.ok).toBe(true)
+    if (!withMarking.ok) return
+    expect(withMarking.invoiceFields.invoice_marking).toBe('KST 4711')
+
+    // Absent/blank input must produce an explicit null (supabase-js drops
+    // undefined keys, and a draft edit that cleared the field relies on NULL
+    // actually being written).
+    const { supabase: supabase2, enqueue: enqueue2 } = createQueuedMockSupabase()
+    enqueue2({ data: { vat_registered: true }, error: null })
+    const withoutMarking = await buildInvoiceWriteData({
+      supabase: supabase2 as unknown as SupabaseClient,
+      companyId: 'company-1',
+      customer,
+      documentType: 'invoice',
+      input: { ...baseHeader, invoice_marking: '   ', items },
+    })
+    expect(withoutMarking.ok).toBe(true)
+    if (!withoutMarking.ok) return
+    expect(withoutMarking.invoiceFields.invoice_marking).toBeNull()
+  })
+
+  it('computes the ROT deduction on the discounted line total', async () => {
+    const { supabase, enqueue } = createQueuedMockSupabase()
+    enqueue({ data: { vat_registered: true }, error: null })
+
+    const customer = makeCustomer({ customer_type: 'individual' })
+    const result = await buildInvoiceWriteData({
+      supabase: supabase as unknown as SupabaseClient,
+      companyId: 'company-1',
+      customer,
+      documentType: 'invoice',
+      input: {
+        ...baseHeader,
+        deduction_personnummer: '199001019802',
+        deduction_housing_designation: 'Testbrand 1:1',
+        items: [
+          {
+            description: 'Renovering arbete',
+            quantity: 10,
+            unit: 'tim',
+            unit_price: 1000,
+            vat_rate: 25,
+            discount_percent: 10,
+            deduction_type: 'rot',
+            work_type: 'BYGG',
+            labor_hours: 10,
+          },
+        ],
+      },
+    })
+
+    expect(result.ok).toBe(true)
+    if (!result.ok) return
+    // Net 9 000 excl VAT -> 11 250 incl VAT -> ROT 30% = 3 375.
+    expect(result.items[0].deduction_amount).toBe(3375)
+    expect(result.invoiceFields.deduction_total).toBe(3375)
+  })
+})
@@ -259,6 +259,71 @@ describe('generatePeppolBisBillingInvoice', () => {
    )
  })

+  it('prefers invoice_marking over your_reference for BT-10 BuyerReference', () => {
+    const input = makeValidInput()
+    input.invoice = makeInvoice({ ...input.invoice, invoice_marking: 'KST 4711' })
+
+    const result = generatePeppolBisBillingInvoice(input)
+
+    expect(result.ok).toBe(true)
+    if (!result.ok) return
+    expect(result.xml).toContain('<cbc:BuyerReference>KST 4711</cbc:BuyerReference>')
+  })
+
+  it('accepts a marking-only invoice (no your_reference) as buyer reference', () => {
+    const input = makeValidInput()
+    input.invoice = makeInvoice({
+      ...input.invoice,
+      your_reference: null,
+      invoice_marking: 'PO-2026-17',
+    })
+
+    const result = generatePeppolBisBillingInvoice(input)
+
+    expect(result.ok).toBe(true)
+    if (!result.ok) return
+    expect(result.xml).toContain('<cbc:BuyerReference>PO-2026-17</cbc:BuyerReference>')
+  })
+
+  it('renders a per-line discount as a BG-27 allowance with net LineExtensionAmount', () => {
+    const input = makeValidInput()
+    // 2 × 100 = 200 gross, 10% discount = 20, net 180, VAT 25% on net = 45.
+    input.items = [
+      makeItem({ discount_percent: 10, line_total: 180, vat_amount: 45 }),
+    ]
+    input.invoice = makeInvoice({
+      ...input.invoice,
+      subtotal: 180,
+      vat_amount: 45,
+      total: 225,
+      remaining_amount: 225,
+    })
+
+    const result = generatePeppolBisBillingInvoice(input)
+
+    expect(result.ok).toBe(true)
+    if (!result.ok) return
+    expect(result.xml).toContain('<cbc:LineExtensionAmount currencyID="SEK">180.00</cbc:LineExtensionAmount>')
+    expect(result.xml).toContain('<cbc:ChargeIndicator>false</cbc:ChargeIndicator>')
+    expect(result.xml).toContain('<cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>')
+    expect(result.xml).toContain('<cbc:MultiplierFactorNumeric>10</cbc:MultiplierFactorNumeric>')
+    expect(result.xml).toContain('<cbc:Amount currencyID="SEK">20.00</cbc:Amount>')
+    expect(result.xml).toContain('<cbc:BaseAmount currencyID="SEK">200.00</cbc:BaseAmount>')
+    // The undiscounted unit price stays in cac:Price (BT-146).
+    expect(result.xml).toContain('<cbc:PriceAmount currencyID="SEK">100</cbc:PriceAmount>')
+  })
+
+  it('rejects a discounted line whose stored total is not net of the discount', () => {
+    const input = makeValidInput()
+    input.items = [makeItem({ discount_percent: 10, line_total: 200, vat_amount: 50 })]
+
+    const result = generatePeppolBisBillingInvoice(input)
+
+    expect(result.ok).toBe(false)
+    if (result.ok) return
+    expect(result.issues.map(({ code }) => code)).toContain('LINE_TOTAL_MISMATCH')
+  })
+
  it('rejects credit notes and self-billed invoices in the generation layer', () => {
    for (const invoice of [
      makeInvoice({
@@ -19,6 +19,7 @@ function makeItem(overrides: Partial<InvoiceWriteItemRow> = {}): InvoiceWriteIte
    quantity: 1,
    unit: 'tim',
    unit_price: 1000,
+    discount_percent: 0,
    line_total: 1000,
    vat_rate: 25,
    vat_amount: 250,
@@ -9,6 +9,10 @@ export function buildCreditNoteItem(invoiceId: string, item: InvoiceItem) {
    quantity: -Math.abs(item.quantity),
    unit: item.unit,
    unit_price: item.unit_price,
+    // Carried so the kreditfaktura's face arithmetic still multiplies out
+    // (antal x a-pris - rabatt = summa) and the PDF shows the same Rabatt
+    // column the original did (ML 17 kap 24 §: prisnedsattningen ska framga).
+    discount_percent: item.discount_percent ?? 0,
    line_total: -Math.abs(item.line_total),
    vat_rate: item.vat_rate ?? 0,
    vat_amount: -(item.vat_amount ? Math.abs(item.vat_amount) : 0),
@@ -2,6 +2,7 @@ import type { SupabaseClient } from '@supabase/supabase-js'
 import type { Currency, Customer, InvoiceDocumentType } from '@/types'
 import { getVatRules, getPermittedVatRates } from '@/lib/invoices/vat-rules'
 import { isBalanceSheetAccount } from '@/lib/invoices/posting-account'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
 import { fetchExchangeRate, convertToSEK } from '@/lib/currency/riksbanken'
 import { DEFAULT_DEFERRED_REVENUE_ACCOUNT } from '@/lib/bookkeeping/accruals/account-suggestions'
 import {
@@ -46,6 +47,9 @@ export interface InvoiceWriteItemInput {
  quantity: number
  unit: string
  unit_price: number
+  /** Percentage discount on the line (0-100). Omitted/null = 0; line_total
+   *  and vat_amount are computed NET of it (lib/invoices/line-amounts.ts). */
+  discount_percent?: number | null
  vat_rate?: number
  article_id?: string | null
  revenue_account?: string | null
@@ -70,6 +74,8 @@ export interface InvoiceWriteInput {
  currency: Currency
  your_reference?: string
  our_reference?: string
+  /** Fakturamärkning: buyer-required marking, separate from your_reference. */
+  invoice_marking?: string
  notes?: string
  /** Optional https payment link (schema-validated). Omitted/empty → null. */
  payment_link_url?: string
@@ -111,6 +117,7 @@ export type InvoiceWriteFields = {
  reverse_charge_text: string | null
  your_reference: string | null | undefined
  our_reference: string | null | undefined
+  invoice_marking: string | null
  notes: string | null | undefined
  payment_link_url: string | null
  payment_link_auto: boolean
@@ -129,6 +136,7 @@ export type InvoiceWriteItemRow = {
  quantity: number
  unit: string
  unit_price: number
+  discount_percent: number
  line_total: number
  vat_rate: number
  vat_amount: number
@@ -224,8 +232,12 @@ export async function buildInvoiceWriteData(params: {
  }

  // Free-text rows carry no amounts and are excluded from totals + VAT.
+  // Line totals are net of any per-line discount (rabatt i procent).
  const subtotal = items.reduce(
-    (sum, item) => (item.line_type === 'text' ? sum : sum + item.quantity * item.unit_price),
+    (sum, item) =>
+      item.line_type === 'text'
+        ? sum
+        : sum + computeLineNet(item.quantity, item.unit_price, item.discount_percent),
    0,
  )

@@ -260,7 +272,7 @@ export async function buildInvoiceWriteData(params: {
          details: { account: item.revenue_account, vatRate: itemRate },
        }
      }
-      const lineTotal = item.quantity * item.unit_price
+      const lineTotal = computeLineNet(item.quantity, item.unit_price, item.discount_percent)
      vatAmount += Math.round(lineTotal * itemRate / 100 * 100) / 100
    }
  }
@@ -330,6 +342,7 @@ export async function buildInvoiceWriteData(params: {
    const validateInput = items.map((item) => ({
      unit_price: item.unit_price,
      quantity: item.quantity,
+      discount_percent: item.discount_percent ?? 0,
      deduction_type: item.deduction_type ?? null,
      // The deduction base is arbetskostnaden inkl. moms (HUSFL 6-9 §§), so
      // the validator and total need the same per-line rate the item rows
@@ -513,6 +526,9 @@ export async function buildInvoiceWriteData(params: {
    reverse_charge_text: notVatRegistered ? null : (headerRules.reverseChargeText || null),
    your_reference: input.your_reference,
    our_reference: input.our_reference,
+    // Always a concrete value so a draft edit that cleared the field NULLs
+    // the column (supabase-js drops undefined keys).
+    invoice_marking: input.invoice_marking?.trim() || null,
    notes: input.notes,
    // Always a concrete value (never undefined) so a draft edit that cleared
    // the field actually NULLs the column: supabase-js drops undefined keys.
@@ -542,6 +558,7 @@ export async function buildInvoiceWriteData(params: {
        quantity: 0,
        unit: '',
        unit_price: 0,
+        discount_percent: 0,
        line_total: 0,
        vat_rate: 0,
        vat_amount: 0,
@@ -561,7 +578,8 @@ export async function buildInvoiceWriteData(params: {
      }
    }
    const itemRate = item.vat_rate !== undefined ? item.vat_rate : vatRules.rate
-    const lineTotal = item.quantity * item.unit_price
+    const discountPercent = item.discount_percent ?? 0
+    const lineTotal = computeLineNet(item.quantity, item.unit_price, discountPercent)
    const itemVat = documentType === 'delivery_note' ? 0 : Math.round(lineTotal * itemRate / 100 * 100) / 100
    // ROT/RUT deduction is recomputed server-side so a tampered client can't
    // expand the 1513 receivable beyond the rules. Non-invoice document types
@@ -571,6 +589,7 @@ export async function buildInvoiceWriteData(params: {
      ? computeDeduction({
          unit_price: item.unit_price,
          quantity: item.quantity,
+          discount_percent: discountPercent,
          deduction_type: deductionType,
          vat_rate: itemRate,
        })
@@ -582,6 +601,7 @@ export async function buildInvoiceWriteData(params: {
      quantity: item.quantity,
      unit: item.unit,
      unit_price: item.unit_price,
+      discount_percent: discountPercent,
      line_total: lineTotal,
      vat_rate: itemRate,
      vat_amount: itemVat,
@@ -22,6 +22,7 @@ export interface InvoiceCopyItem {
  quantity: number
  unit: string
  unit_price: number
+  discount_percent: number
  vat_rate: number
  article_id: null
  revenue_account: string | null
@@ -85,6 +86,8 @@ export function buildInvoiceCopyInitial(source: InvoiceCopySource): InvoiceCopyI
        quantity: item.quantity,
        unit: item.unit,
        unit_price: item.unit_price,
+        // Agreed price reduction is reusable commercial content, like the price.
+        discount_percent: item.discount_percent ?? 0,
        vat_rate: item.vat_rate ?? 25,
        // A copied line keeps the frozen description and price, but is not
        // linked to a possibly changed or archived article preset.
@@ -0,0 +1,60 @@
+import { roundOre } from '@/lib/money'
+
+/**
+ * Shared per-line amount math for invoice items with an optional percentage
+ * discount (rabatt i procent per artikelrad).
+ *
+ * The formula set is deliberately exact in öre so every surface (editor
+ * preview, build-invoice-write, staged-operation commit, PDF, Peppol BG-27
+ * line allowance) agrees to the öre:
+ *
+ *   gross    = roundOre(quantity * unit_price)
+ *   discount = roundOre(gross * discount_percent / 100)
+ *   net      = roundOre(gross - discount)
+ *
+ * `net` is what is stored as invoice_items.line_total and what VAT is
+ * computed on (the discount reduces the beskattningsunderlag, ML 8 kap 13 §).
+ * Because `discount` is rounded before the subtraction, gross - discount is
+ * exact 2-decimal arithmetic and the UBL line check
+ * LineExtensionAmount = base - allowance holds without a tolerance.
+ *
+ * A line with no discount keeps the legacy unrounded `quantity * unit_price`
+ * as its net so existing invoices, stored line_totals and the Peppol
+ * LINE_TOTAL_MISMATCH check stay byte-identical.
+ */
+export interface LineAmounts {
+  /** Line amount before discount (rounded to öre when a discount applies). */
+  gross: number
+  /** Discount amount in invoice currency (0 when no discount). */
+  discount: number
+  /** Line amount after discount: what line_total stores and VAT applies to. */
+  net: number
+}
+
+/** True when the value is a discount that actually changes the line. */
+export function hasLineDiscount(discountPercent: number | null | undefined): boolean {
+  return typeof discountPercent === 'number' && discountPercent > 0
+}
+
+export function computeLineAmounts(
+  quantity: number,
+  unitPrice: number,
+  discountPercent?: number | null,
+): LineAmounts {
+  const raw = (quantity || 0) * (unitPrice || 0)
+  if (!hasLineDiscount(discountPercent)) {
+    return { gross: raw, discount: 0, net: raw }
+  }
+  const gross = roundOre(raw)
+  const discount = roundOre((gross * (discountPercent as number)) / 100)
+  return { gross, discount, net: roundOre(gross - discount) }
+}
+
+/** Convenience: the net line total (what invoice_items.line_total stores). */
+export function computeLineNet(
+  quantity: number,
+  unitPrice: number,
+  discountPercent?: number | null,
+): number {
+  return computeLineAmounts(quantity, unitPrice, discountPercent).net
+}
@@ -55,6 +55,7 @@ const LABELS = {
    deliveryDate: 'Leveransdatum:',
    yourReference: 'Er referens:',
    ourReference: 'Vår referens:',
+    invoiceMarking: 'Märkning:',
    // Customer box
    custNo: 'Kundnr:',
    orgNo: 'Org.nr:',
@@ -64,6 +65,7 @@ const LABELS = {
    colQty: 'Antal',
    colUnit: 'Enhet',
    colUnitPrice: 'à-pris',
+    colDiscount: 'Rabatt',
    colVat: 'Moms',
    colTotal: 'Summa',
    // Totals
@@ -136,6 +138,7 @@ const LABELS = {
    deliveryDate: 'Delivery date:',
    yourReference: 'Your reference:',
    ourReference: 'Our reference:',
+    invoiceMarking: 'Buyer reference:',
    custNo: 'Customer no.:',
    orgNo: 'Reg. no.:',
    vat: 'VAT:',
@@ -143,6 +146,7 @@ const LABELS = {
    colQty: 'Qty',
    colUnit: 'Unit',
    colUnitPrice: 'Unit price',
+    colDiscount: 'Discount',
    colVat: 'VAT',
    colTotal: 'Amount',
    subtotal: 'Subtotal:',
@@ -367,6 +371,10 @@ function createStyles(branding?: InvoiceBranding) {
      flex: 1.5,
      textAlign: 'right',
    },
+    colDiscount: {
+      flex: 1,
+      textAlign: 'right',
+    },
    colVat: {
      flex: 1,
      textAlign: 'right',
@@ -785,6 +793,10 @@ export function InvoicePDF({ invoice, customer, items, company, originalInvoiceN
    ? new Set(billableItems.map((item) => item.vat_rate))
    : new Set<number>()
  const showVatColumn = hasPerLineVat && uniqueRates.size > 1
+  // Rabatt column only when some line actually carries a discount: the
+  // stored line_total is already net, so the column documents the reduction
+  // (ML 17 kap 24 § p.10: prisnedsättning ska framgå av fakturan).
+  const showDiscountColumn = billableItems.some((item) => (item.discount_percent ?? 0) > 0)

  // Calculate per-rate VAT breakdown for totals
  const vatByRate = hasPerLineVat
@@ -950,6 +962,18 @@ export function InvoicePDF({ invoice, customer, items, company, originalInvoiceN
                </View>
              </View>
            )}
+            {/* Fakturamärkning: one buyer-required marking string, never
+                comma-split (a PO/cost-center label may contain commas). */}
+            {invoice.invoice_marking && (
+              <View style={{ marginBottom: 4 }}>
+                <Text style={styles.label}>{L.invoiceMarking}</Text>
+                <View style={{ flexDirection: 'row', flexWrap: 'wrap', gap: 4, marginTop: 2 }}>
+                  <Text style={{ backgroundColor: '#f0f0f0', borderRadius: 3, paddingHorizontal: 6, paddingVertical: 2, fontSize: 9, fontWeight: 'bold' }}>
+                    {invoice.invoice_marking.trim()}
+                  </Text>
+                </View>
+              </View>
+            )}
          </View>

          {/* Customer */}
@@ -1003,6 +1027,9 @@ export function InvoicePDF({ invoice, customer, items, company, originalInvoiceN
              {!isDeliveryNote && (
                <Text style={[styles.colPrice, styles.tableHeaderText]}>{L.colUnitPrice}</Text>
              )}
+              {!isDeliveryNote && showDiscountColumn && (
+                <Text style={[styles.colDiscount, styles.tableHeaderText]}>{L.colDiscount}</Text>
+              )}
              {!isDeliveryNote && showVatColumn && (
                <Text style={[styles.colVat, styles.tableHeaderText]}>{L.colVat}</Text>
              )}
@@ -1029,6 +1056,11 @@ export function InvoicePDF({ invoice, customer, items, company, originalInvoiceN
                  {!isDeliveryNote && (
                    <Text style={styles.colPrice}>{formatPdfCurrency(item.unit_price, invoice.currency, lang)}</Text>
                  )}
+                  {!isDeliveryNote && showDiscountColumn && (
+                    <Text style={styles.colDiscount}>
+                      {(item.discount_percent ?? 0) > 0 ? `${item.discount_percent}%` : ''}
+                    </Text>
+                  )}
                  {!isDeliveryNote && showVatColumn && (
                    <Text style={styles.colVat}>{item.vat_rate ?? 0}%</Text>
                  )}
@@ -4,6 +4,7 @@ import {
  validatePlusgiroNumber,
 } from '@/lib/bankgiro/luhn'
 import { isSaneDateString, normalizeOrgNumber } from '@/lib/invariants'
+import { computeLineAmounts, hasLineDiscount } from '@/lib/invoices/line-amounts'
 import { getDisplayTotal } from '@/lib/invoices/rounding'
 import { equalOre, roundOre } from '@/lib/money'
 import type { CompanySettings, Customer, Invoice, InvoiceItem } from '@/types'
@@ -270,11 +271,13 @@ function prepareInvoice(input: PeppolInvoiceInput):
      'Invoice, due, and delivery dates must be valid dates.',
    ))
  }
-  if (!hasText(invoice.your_reference)) {
+  // BT-10 BuyerReference: fakturamärkning wins when set (SFTI convention:
+  // the buyer's routing/marking string), else Er referens.
+  if (!hasText(invoice.invoice_marking) && !hasText(invoice.your_reference)) {
    issues.push(validationIssue(
      'BUYER_REFERENCE_REQUIRED', 'invoice.your_reference',
-      'Er referens krävs för Peppol när inköpsordernummer saknas.',
-      'Buyer reference is required for Peppol when no purchase order reference is available.',
+      'Märkning eller Er referens krävs för Peppol när inköpsordernummer saknas.',
+      'A marking or buyer reference is required for Peppol when no purchase order reference is available.',
    ))
  }
  if ((invoice.deduction_total ?? 0) !== 0) {
@@ -396,11 +399,22 @@ function prepareInvoice(input: PeppolInvoiceInput):
        `The VAT rate on invoice line ${index + 1} must be 6, 12, or 25 percent.`,
      ))
    }
-    if (!equalMoney(item.line_total, roundMoney(item.quantity * item.unit_price))) {
+    // Net of any line discount: line_total must equal (qty × price) − rabatt,
+    // the same exact öre arithmetic the write path stores
+    // (lib/invoices/line-amounts.ts) and the BG-27 allowance below renders.
+    const expectedAmounts = computeLineAmounts(item.quantity, item.unit_price, item.discount_percent)
+    if (!equalMoney(item.line_total, roundMoney(expectedAmounts.net))) {
      issues.push(validationIssue(
        'LINE_TOTAL_MISMATCH', `${lineField}.line_total`,
-        `Beloppet på fakturarad ${index + 1} stämmer inte med antal gånger pris.`,
-        `The amount on invoice line ${index + 1} does not equal quantity times price.`,
+        `Beloppet på fakturarad ${index + 1} stämmer inte med antal gånger pris minus rabatt.`,
+        `The amount on invoice line ${index + 1} does not equal quantity times price less discount.`,
+      ))
+    }
+    if (item.discount_percent !== undefined && (item.discount_percent < 0 || item.discount_percent > 100)) {
+      issues.push(validationIssue(
+        'LINE_DISCOUNT_INVALID', `${lineField}.discount_percent`,
+        `Rabatten på fakturarad ${index + 1} måste vara mellan 0 och 100 procent.`,
+        `The discount on invoice line ${index + 1} must be between 0 and 100 percent.`,
      ))
    }
    if (!equalMoney(item.vat_amount, roundMoney(item.line_total * item.vat_rate / 100))) {
@@ -552,11 +566,29 @@ function renderInvoiceXml(input: PeppolInvoiceInput, prepared: PreparedInvoice):
    '      </cac:TaxCategory>',
    '    </cac:TaxSubtotal>',
  ])
-  const invoiceLines = prepared.productItems.flatMap((item, index) => [
+  const invoiceLines = prepared.productItems.flatMap((item, index) => {
+    // Line discount as a BG-27 allowance: LineExtensionAmount stays the net
+    // line_total and the allowance documents base − amount = net exactly
+    // (the amounts come from the same öre arithmetic as the stored total).
+    const amounts = computeLineAmounts(item.quantity, item.unit_price, item.discount_percent)
+    const allowance = hasLineDiscount(item.discount_percent)
+      ? [
+          '    <cac:AllowanceCharge>',
+          '      <cbc:ChargeIndicator>false</cbc:ChargeIndicator>',
+          '      <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>',
+          '      <cbc:AllowanceChargeReason>Rabatt</cbc:AllowanceChargeReason>',
+          `      <cbc:MultiplierFactorNumeric>${formatDecimal(item.discount_percent as number)}</cbc:MultiplierFactorNumeric>`,
+          `      <cbc:Amount currencyID="SEK">${formatMoney(amounts.discount)}</cbc:Amount>`,
+          `      <cbc:BaseAmount currencyID="SEK">${formatMoney(amounts.gross)}</cbc:BaseAmount>`,
+          '    </cac:AllowanceCharge>',
+        ]
+      : []
+    return [
    '  <cac:InvoiceLine>',
    `    <cbc:ID>${index + 1}</cbc:ID>`,
    `    <cbc:InvoicedQuantity unitCode="${UNIT_CODES[item.unit]}">${formatDecimal(item.quantity)}</cbc:InvoicedQuantity>`,
    `    <cbc:LineExtensionAmount currencyID="SEK">${formatMoney(item.line_total)}</cbc:LineExtensionAmount>`,
+    ...allowance,
    '    <cac:Item>',
    `      <cbc:Name>${escapeXml(item.description.trim())}</cbc:Name>`,
    '      <cac:ClassifiedTaxCategory>',
@@ -569,7 +601,8 @@ function renderInvoiceXml(input: PeppolInvoiceInput, prepared: PreparedInvoice):
    `      <cbc:PriceAmount currencyID="SEK">${formatDecimal(item.unit_price)}</cbc:PriceAmount>`,
    '    </cac:Price>',
    '  </cac:InvoiceLine>',
-  ])
+    ]
+  })

  return [
    '<?xml version="1.0" encoding="UTF-8"?>',
@@ -584,7 +617,7 @@ function renderInvoiceXml(input: PeppolInvoiceInput, prepared: PreparedInvoice):
    '  <cbc:InvoiceTypeCode>380</cbc:InvoiceTypeCode>',
    invoice.notes ? `  <cbc:Note>${escapeXml(invoice.notes)}</cbc:Note>` : null,
    '  <cbc:DocumentCurrencyCode>SEK</cbc:DocumentCurrencyCode>',
-    `  <cbc:BuyerReference>${escapeXml(invoice.your_reference?.trim() ?? '')}</cbc:BuyerReference>`,
+    `  <cbc:BuyerReference>${escapeXml((invoice.invoice_marking?.trim() || invoice.your_reference?.trim()) ?? '')}</cbc:BuyerReference>`,
    renderParty('AccountingSupplierParty', prepared.supplier, company.f_skatt),
    renderParty('AccountingCustomerParty', prepared.buyer, false),
    invoice.delivery_date
@@ -1,4 +1,5 @@
 import { roundOre } from '@/lib/money'
+import { computeLineNet } from '@/lib/invoices/line-amounts'

 /**
 * ROT/RUT-avdrag rules.
@@ -211,6 +212,12 @@ export interface ItemForDeduction {
  unit_price: number
  /** Quantity. Same field as invoice_items.quantity. */
  quantity: number
+  /**
+   * Percentage discount on the line (0-100), invoice_items.discount_percent.
+   * The deduction base is the amount the customer actually pays, so a
+   * discounted line deducts on the NET line total. Omitted/null = 0.
+   */
+  discount_percent?: number | null
  /** 'rot' | 'rut' | null. Drives whether the deduction kicks in at all. */
  deduction_type?: DeductionType | null
  /**
@@ -242,7 +249,8 @@ export interface ItemForDeduction {
 */
 export function computeDeduction(item: ItemForDeduction): number {
  if (!item.deduction_type) return 0
-  const lineTotal = item.unit_price * item.quantity
+  // Net of any line discount: the deduction follows what the customer pays.
+  const lineTotal = computeLineNet(item.quantity, item.unit_price, item.discount_percent)
  if (lineTotal <= 0) return 0
  const rate = item.vat_rate ?? 0
  const lineVat = rate > 0 ? Math.round(lineTotal * rate / 100 * 100) / 100 : 0
@@ -168,6 +168,7 @@ import {
  type InvoiceWriteInput,
  type InvoiceWriteItemInput,
 } from '@/lib/invoices/build-invoice-write'
+import { computeLineNet } from '@/lib/invoices/line-amounts'
 import { deleteDraftInvoice } from '@/lib/invoices/delete-draft-invoice'
 import { isEditableInvoiceDraft } from '@/lib/invoices/is-editable-draft'
 import { replaceInvoiceItems } from '@/lib/invoices/replace-invoice-items'
@@ -1631,6 +1632,7 @@ async function commitCreateInvoice(
  const customerId = params.customer_id as string
  const items = params.items as Array<{
    description: string; quantity: number; unit: string; unit_price: number; vat_rate?: number
+    discount_percent?: number | null
    article_id?: string | null; revenue_account?: string | null
    line_type?: 'product' | 'text'
    dimensions?: Record<string, string>
@@ -1674,7 +1676,12 @@ async function commitCreateInvoice(
  const notVatRegistered = vatSettings?.vat_registered === false
  if (notVatRegistered) for (const item of items) item.vat_rate = 0

-  const subtotal = billableItems.reduce((sum, item) => sum + item.quantity * item.unit_price, 0)
+  // Line totals net of any per-line discount, same math as the web path
+  // (lib/invoices/line-amounts.ts).
+  const subtotal = billableItems.reduce(
+    (sum, item) => sum + computeLineNet(item.quantity, item.unit_price, item.discount_percent),
+    0,
+  )

  let vatAmount = 0
  for (const item of billableItems) {
@@ -1682,7 +1689,14 @@ async function commitCreateInvoice(
    if (!allowedRates.has(itemRate)) {
      return { error: `Momssats ${itemRate}% är inte tillåten för denna kundtyp`, status: 400 }
    }
-    const lineTotal = item.quantity * item.unit_price
+    // Strict typeof: staged params are JSON a tampered client could shape;
+    // a string would coerce past a bare range check but be ignored by the
+    // number-typed totals math, then land in the NUMERIC column anyway.
+    const discountPercent = item.discount_percent ?? 0
+    if (typeof discountPercent !== 'number' || !(discountPercent >= 0 && discountPercent <= 100)) {
+      return { error: 'Rabatten per rad måste vara mellan 0 och 100 procent', status: 400 }
+    }
+    const lineTotal = computeLineNet(item.quantity, item.unit_price, discountPercent)
    vatAmount += Math.round(lineTotal * itemRate / 100 * 100) / 100
  }

@@ -1824,6 +1838,7 @@ async function commitCreateInvoice(
      reverse_charge_text: notVatRegistered ? null : (vatRules.reverseChargeText || null),
      our_reference: (params.our_reference as string) || null,
      your_reference: (params.your_reference as string) || null,
+      invoice_marking: (params.invoice_marking as string) || null,
      notes: (params.notes as string) || null,
      payment_link_url: paymentLinkUrl,
      default_dimensions: defaultDimensions ?? {},
@@ -1846,6 +1861,7 @@ async function commitCreateInvoice(
        quantity: 0,
        unit: '',
        unit_price: 0,
+        discount_percent: 0,
        line_total: 0,
        vat_rate: 0,
        vat_amount: 0,
@@ -1855,7 +1871,8 @@ async function commitCreateInvoice(
      }
    }
    const itemRate = item.vat_rate !== undefined ? item.vat_rate : vatRules.rate
-    const lineTotal = item.quantity * item.unit_price
+    const discountPercent = item.discount_percent ?? 0
+    const lineTotal = computeLineNet(item.quantity, item.unit_price, discountPercent)
    const itemVat = Math.round(lineTotal * itemRate / 100 * 100) / 100
    return {
      invoice_id: invoice.id,
@@ -1865,6 +1882,7 @@ async function commitCreateInvoice(
      quantity: item.quantity,
      unit: item.unit,
      unit_price: item.unit_price,
+      discount_percent: discountPercent,
      line_total: lineTotal,
      vat_rate: itemRate,
      vat_amount: itemVat,
@@ -1942,7 +1960,7 @@ async function commitUpdateInvoice(
  const { data: existing, error: fetchError } = await supabase
    .from('invoices')
    .select(
-      'id, status, invoice_number, journal_entry_id, is_self_billed, credited_invoice_id, customer_id, document_type, invoice_date, due_date, delivery_date, currency, your_reference, our_reference, notes, payment_link_url, payment_link_auto, ore_rounding, default_dimensions, deduction_personnummer_encrypted, deduction_personnummer_last4',
+      'id, status, invoice_number, journal_entry_id, is_self_billed, credited_invoice_id, customer_id, document_type, invoice_date, due_date, delivery_date, currency, your_reference, our_reference, invoice_marking, notes, payment_link_url, payment_link_auto, ore_rounding, default_dimensions, deduction_personnummer_encrypted, deduction_personnummer_last4',
    )
    .eq('id', invoiceId)
    .eq('company_id', companyId)
@@ -2003,7 +2021,7 @@ async function commitUpdateInvoice(
    const { data: itemRows, error: itemsFetchError } = await supabase
      .from('invoice_items')
      .select(
-        'line_type, description, quantity, unit, unit_price, vat_rate, article_id, revenue_account, deduction_type, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, accrual_period_start, accrual_period_end, accrual_balance_account, dimensions',
+        'line_type, description, quantity, unit, unit_price, discount_percent, vat_rate, article_id, revenue_account, deduction_type, labor_hours, work_type, housing_designation, apartment_number, brf_org_number, accrual_period_start, accrual_period_end, accrual_balance_account, dimensions',
      )
      .eq('invoice_id', invoiceId)
      .order('sort_order', { ascending: true })
@@ -2028,6 +2046,7 @@ async function commitUpdateInvoice(
    currency: existing.currency as Currency,
    your_reference: changes.your_reference ?? existing.your_reference ?? undefined,
    our_reference: changes.our_reference ?? existing.our_reference ?? undefined,
+    invoice_marking: changes.invoice_marking ?? existing.invoice_marking ?? undefined,
    notes: changes.notes ?? existing.notes ?? undefined,
    // Not editable through this operation: fed back so the builder echoes the
    // stored values instead of clearing them.
@@ -4553,6 +4572,7 @@ async function commitCreditInvoice(
      reverse_charge_text: original.reverse_charge_text,
      your_reference: original.your_reference,
      our_reference: original.our_reference,
+      invoice_marking: original.invoice_marking ?? null,
      notes: reason || `Krediterar faktura ${original.invoice_number}`,
      credited_invoice_id: id,
      // Dimensions PR7: copy so the reversal nets against the same cells.
@@ -4573,6 +4593,7 @@ async function commitCreditInvoice(
    quantity: number
    unit: string
    unit_price: number
+    discount_percent?: number | null
    line_total: number
    vat_rate?: number
    vat_amount?: number
@@ -4587,6 +4608,8 @@ async function commitCreditInvoice(
    quantity: -Math.abs(item.quantity),
    unit: item.unit,
    unit_price: item.unit_price,
+    // Kreditfakturans face arithmetic must multiply out like the original's.
+    discount_percent: item.discount_percent ?? 0,
    line_total: -Math.abs(item.line_total),
    vat_rate: item.vat_rate ?? 0,
    vat_amount: -(item.vat_amount ? Math.abs(item.vat_amount) : 0),
@@ -23,6 +23,8 @@ const InvoiceChangesSchema = z
    delivery_date: isoDate.nullable().optional(),
    your_reference: z.string().optional(),
    our_reference: z.string().optional(),
+    // Fakturamärkning: buyer-required marking, separate from your_reference.
+    invoice_marking: z.string().max(200).optional(),
    items: z.array(CreateInvoiceItemSchema).min(1, 'At least one item is required').optional(),
    // Replaces the whole bag; {} clears all tags.
    default_dimensions: DimensionsBagSchema.optional(),
@@ -3813,6 +3813,7 @@
    "chip_received": "Received {date}",
    "chip_delivery": "Delivery date {date}",
    "chip_your_reference": "Your reference: {reference}",
+    "chip_invoice_marking": "Marking: {marking}",
    "chip_stripe_auto": "Stripe link created on send",
    "chip_payment_link": "Payment link added",
    "chip_ore_off": "No öre rounding",
@@ -3831,6 +3832,10 @@
    "ready_create": "Ready to review: everything else has sensible defaults.",
    "ready_edit": "Ready to save.",
    "ready_self_billed": "Ready to register.",
+    "row_menu_add_discount": "Add discount",
+    "row_menu_remove_discount": "Remove discount",
+    "discount_label": "Discount",
+    "validation_discount_range": "The discount must be between 0 and 100 percent",
    "row_menu_set_account": "Set posting account",
    "row_menu_remove_account": "Remove posting account",
    "row_menu_set_dimensions": "Set cost centre/project",
@@ -3899,6 +3904,8 @@
    "your_reference_placeholder": "Customer contact person",
    "our_reference_label": "Our reference",
    "our_reference_placeholder": "Your name",
+    "invoice_marking_label": "Marking",
+    "invoice_marking_placeholder": "E.g. cost center or order no.",
    "payment_link_label": "Payment link (optional)",
    "payment_link_placeholder": "https://buy.stripe.com/…",
    "payment_link_hint": "Paste a payment link created for this specific invoice (e.g. in Stripe). Make sure the amount matches and preferably limit the link to a single payment. The link is shown as a button in the invoice email and as a QR code on the PDF.",
@@ -4015,6 +4022,7 @@
    "total": "Total",
    "your_reference": "Your reference:",
    "our_reference": "Our reference:",
+    "invoice_marking": "Marking:",
    "notes_prefix": "Note: {notes}"
  },
  "invoice_bank_setup": {
@@ -3813,6 +3813,7 @@
    "chip_received": "Mottagen {date}",
    "chip_delivery": "Leveransdatum {date}",
    "chip_your_reference": "Er referens: {reference}",
+    "chip_invoice_marking": "Märkning: {marking}",
    "chip_stripe_auto": "Stripe-länk skapas vid utskick",
    "chip_payment_link": "Betalningslänk inlagd",
    "chip_ore_off": "Ingen öresavrundning",
@@ -3831,6 +3832,10 @@
    "ready_create": "Klar att granska: allt annat har smarta förval.",
    "ready_edit": "Klart att spara.",
    "ready_self_billed": "Klar att registrera.",
+    "row_menu_add_discount": "Lägg till rabatt",
+    "row_menu_remove_discount": "Ta bort rabatt",
+    "discount_label": "Rabatt",
+    "validation_discount_range": "Rabatten måste vara mellan 0 och 100 procent",
    "row_menu_set_account": "Ange bokföringskonto",
    "row_menu_remove_account": "Ta bort bokföringskonto",
    "row_menu_set_dimensions": "Ange kostnadsställe/projekt",
@@ -3899,6 +3904,8 @@
    "your_reference_placeholder": "Kontaktperson hos kund",
    "our_reference_label": "Vår referens",
    "our_reference_placeholder": "Ditt namn",
+    "invoice_marking_label": "Märkning",
+    "invoice_marking_placeholder": "T.ex. kostnadsställe eller ordernr",
    "payment_link_label": "Betalningslänk (valfritt)",
    "payment_link_placeholder": "https://buy.stripe.com/…",
    "payment_link_hint": "Klistra in en betalningslänk skapad för just denna faktura (t.ex. i Stripe). Kontrollera att beloppet stämmer och begränsa gärna länken till en betalning. Länken visas som en knapp i fakturamejlet och som QR-kod på PDF:en.",
@@ -4015,6 +4022,7 @@
    "total": "Totalt",
    "your_reference": "Er referens:",
    "our_reference": "Vår referens:",
+    "invoice_marking": "Märkning:",
    "notes_prefix": "Anteckning: {notes}"
  },
  "invoice_bank_setup": {
@@ -110,6 +110,7 @@ Request body:
  document_type?: "invoice" | "proforma" | "delivery_note",
  your_reference?: string,
  our_reference?: string,
+  invoice_marking?: string,
  notes?: string,
  payment_link_url?: string | "",
  payment_link_auto?: boolean,
@@ -124,7 +125,7 @@ Request body:
  external_invoice_number?: string | "",
  self_billing_agreement_ref?: string,
  received_date?: string | "",
-  items: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[]
+  items: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, discount_percent?: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[]
 }
 ```

@@ -305,7 +306,7 @@ Request body:
  our_reference?: string | unknown,
  notes?: string | unknown,
  default_dimensions?: Record<string, string>,
-  items?: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[]
+  items?: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, discount_percent?: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[]
 }
 ```

@@ -776,7 +777,7 @@ Bulk-creation endpoint. Each invoice in the request array is validated and inser
 Request body:
 ```ts
 {
-  invoices: { customer_id: string, invoice_date: string, due_date: string, delivery_date?: string | "", currency: "SEK" | "EUR" | "USD" | "GBP" | "NOK" | "DKK", document_type?: "invoice" | "proforma" | "delivery_note", your_reference?: string, our_reference?: string, notes?: string, payment_link_url?: string | "", payment_link_auto?: boolean, deduction_personnummer?: string, deduction_housing_designation?: string, deduction_apartment_number?: string, deduction_brf_org_number?: string | "", save_as_draft?: boolean, ore_rounding?: boolean, default_dimensions?: Record<string, string>, is_self_billed?: boolean, external_invoice_number?: string | "", self_billing_agreement_ref?: string, received_date?: string | "", items: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[] }[],
+  invoices: { customer_id: string, invoice_date: string, due_date: string, delivery_date?: string | "", currency: "SEK" | "EUR" | "USD" | "GBP" | "NOK" | "DKK", document_type?: "invoice" | "proforma" | "delivery_note", your_reference?: string, our_reference?: string, invoice_marking?: string, notes?: string, payment_link_url?: string | "", payment_link_auto?: boolean, deduction_personnummer?: string, deduction_housing_designation?: string, deduction_apartment_number?: string, deduction_brf_org_number?: string | "", save_as_draft?: boolean, ore_rounding?: boolean, default_dimensions?: Record<string, string>, is_self_billed?: boolean, external_invoice_number?: string | "", self_billing_agreement_ref?: string, received_date?: string | "", items: { line_type?: "product" | "text", description: string, quantity: number, unit: string, unit_price: number, discount_percent?: number, vat_rate?: number, article_id?: string, revenue_account?: string, deduction_type?: "rot" | "rut", labor_hours?: number, work_type?: string, housing_designation?: string, apartment_number?: string, brf_org_number?: string | "", accrual_period_start?: string, accrual_period_end?: string, accrual_balance_account?: string, dimensions?: Record<string, string> }[] }[],
  all_or_nothing?: boolean
 }
 ```
@@ -0,0 +1,30 @@
+-- Per-line percentage discount (rabatt i procent per artikelrad) and a
+-- fakturamärkning field separate from Er referens (your_reference).
+--
+-- invoice_items.discount_percent: 0-100, default 0. The stored line_total is
+-- always the NET amount (after discount); VAT is computed on the net, so the
+-- bookkeeping generators need no change. Server code recomputes the discount
+-- via lib/invoices/line-amounts.ts and never trusts a client-sent total.
+--
+-- invoices.invoice_marking: the buyer-required marking (kostnadsstalle,
+-- project code, PO label) printed on the invoice and mapped to Peppol BT-10
+-- BuyerReference when set. Distinct from your_reference, which stays the
+-- contact person (Er referens).
+
+ALTER TABLE public.invoice_items
+  ADD COLUMN IF NOT EXISTS discount_percent NUMERIC NOT NULL DEFAULT 0;
+
+ALTER TABLE public.invoice_items DROP CONSTRAINT IF EXISTS invoice_items_discount_percent_check;
+ALTER TABLE public.invoice_items ADD CONSTRAINT invoice_items_discount_percent_check
+  CHECK (discount_percent >= 0 AND discount_percent <= 100);
+
+COMMENT ON COLUMN public.invoice_items.discount_percent IS
+  'Percentage discount on the line (0-100). line_total and vat_amount are stored net of this discount.';
+
+ALTER TABLE public.invoices
+  ADD COLUMN IF NOT EXISTS invoice_marking TEXT;
+
+COMMENT ON COLUMN public.invoices.invoice_marking IS
+  'Fakturamarkning: buyer-required marking (cost center/project/PO), separate from your_reference (Er referens). Feeds Peppol BT-10 BuyerReference when set.';
+
+NOTIFY pgrst, 'reload schema';
@@ -1267,6 +1267,11 @@ export interface Invoice {
  // Reference
  your_reference: string | null
  our_reference: string | null
+  // Fakturamärkning: buyer-required marking (cost center, project, PO label),
+  // separate from your_reference (Er referens = contact person). Printed on
+  // the PDF and mapped to Peppol BT-10 BuyerReference when set. Optional in
+  // TS for pre-migration fixtures.
+  invoice_marking?: string | null

  // Optional online payment link (pasted by the user, e.g. a Stripe Payment
  // Link). Rendered as a "Betala online" button in the invoice email and as a
@@ -1431,7 +1436,12 @@ export interface InvoiceItem {
  // Price
  unit_price: number

-  // Calculated
+  // Percentage discount on the line (0-100). line_total and vat_amount are
+  // stored NET of this discount (lib/invoices/line-amounts.ts). Optional in
+  // TS for pre-migration fixtures; treat undefined the same as 0.
+  discount_percent?: number
+
+  // Calculated (net of discount_percent)
  line_total: number

  // Per-line VAT
@@ -1708,6 +1718,8 @@ export interface CreateInvoiceInput {
  document_type?: InvoiceDocumentType
  your_reference?: string
  our_reference?: string
+  /** Fakturamärkning: buyer-required marking, separate from your_reference. */
+  invoice_marking?: string
  notes?: string
  /** Optional https link where the customer can pay online (e.g. a Stripe Payment Link). */
  payment_link_url?: string
@@ -1731,6 +1743,8 @@ export interface CreateInvoiceItemInput {
  quantity: number
  unit: string
  unit_price: number
+  /** Percentage discount on the line (0-100). Omitted/null = 0. */
+  discount_percent?: number | null
  vat_rate?: number
  /** Source article (optional). Free-text lines omit it. */
  article_id?: string | null