feat(vat): oss momskod keeps unionsordningen sales out of the momsdeklaration (#1797)

A Fortnox user with OSS sales hit the SIE import mapping step and found no
way to map OSS accounts: the momskod picker had no OSS option, 3106-style
labels ("Försäljning varor till annat EU-land, momspliktig") were suggested
as EU-varor (ruta 35), and an OSS revenue account with a sats set leaked into
ruta 05. Skatteverket: "Den försäljning som du redovisar i OSS ska du inte
redovisa i den vanliga momsdeklarationen."

- add the 'oss' revenue treatment: allowed for class 3 only, mapped to no
  ruta, default rate null (destination-country rate is not a Swedish sats);
  explicit 'oss' also overrides static BAS mappings such as 3001
- REVENUE_RUTA becomes a partial map where null = allowed but off the
  declaration, so the class gate no longer conflates "no ruta" with
  "purchase-only"
- SIE label suggestion: OSS/unionsordningen labels suggest 'oss';
  momspliktig EU-varor labels are left for review instead of ruta 35
- AccountVatTreatmentSchema derives from ACCOUNT_VAT_TREATMENTS instead of a
  second literal list
- migration widens the class-aware CHECK with 'oss' for class 3 (superset;
  NOT VALID + VALIDATE like its predecessor); pg test extended
- sv/en labels; unit tests for resolver, suggestion, declaration exclusion

Per-country VAT rates on invoices and the quarterly EUR/ECB OSS underlag
remain unbuilt (DECISIONS.md).


Claude-Session: https://claude.ai/code/session_01E3QB8GxJ9tS217agHjLRk7

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

DECISIONS.md

@@ -1157,3 +1157,4 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-21] Behandlingshistorik ships as a report over existing stores (journal_entries.committed_at + audit_log + rattelse log + import tables) rather than on processing_history: that table only carries Document/BankTransaction/System events in prod, while audit_log is complete, immutable and already the archive's revision/behandlingshistorik.json. Event labels stay Swedish in both locales (räkenskapsinformation, archived 7 years, same rule as SIE/grundbok); only the view chrome is translated. Bokföringsposter come from journal_entries (not audit COMMIT rows) so entries predating the audit log or from the July SIE-import window are never missing.
 [2026-08-21] Peppol access is granted per company by the operators, never self-served (peppol_access table, locked by default): every transmission is billed per document by Qvalia and every receiving identifier consumes a contracted tenant slot, so the company asks from Settings > Fakturering (request row + e-mail to support) and we enable it with scripts/peppol/access.ts, setting max_sends (null = no cap) and separately receive_enabled; the send route refuses PEPPOL_ACCESS_REQUIRED / PEPPOL_SEND_LIMIT_REACHED before touching the invoice, and registration refuses PEPPOL_RECEIVING_NOT_ENABLED. Founder call 2026-08-21 after the first open-for-all hour in prod.
 [2026-08-22] BoXon feedback fix: leftover assistant proposals no longer need manual cleanup in Granskning. lib/agent/pending/reject-conversation-pending.ts rejects a conversation's still-pending pending_operations in one update (guarded on status='pending' so it never stamps 'rejected' over a committing/committed verifikat; company-scoped; filtered by agent_metadata->>conversation_id). Surfaced two ways: POST /api/agent/conversations/[id]/reject-pending (the chat's "Rensa förslag som inte godkänts" button) + auto-clear when the conversation is ARCHIVED (best-effort in the PATCH; archive = "I'm done with this thread"). Kept durable-by-default (proposals still resume) — the button is explicit user intent, not an auto-reject on every panel close, so resume still works. Chat button drops all staged cards from view on click (committed ones are already booked; the card was only a confirmation). UI PR: needs founder visual sign-off on the button.
+[2026-08-22] OSS support = one `oss` revenue momskod (off every ruta) + SIE-import label suggestion, not per-country invoice rates or an EUR/ECB OSS report: Skatteverket requires OSS sales out of the ordinary momsdeklaration, and the missing piece a Fortnox OSS user hits first is the mapping step (3106-style labels were pushed to ruta 35, OSS-named accounts had no option). Per-country VAT rates on invoices and the quarterly EUR underlag are a separate feature; the recommended interim workflow is one revenue account per country/rate (as Fortnox suggests) + Huvudbok per kvartal + manual ECB conversion.

lib/api/schemas.ts

@@ -1,6 +1,7 @@
 import { z } from 'zod'
 import { normaliseSwish, isValidSwish } from '@/lib/payments/swish'
 import { normalizeVatNumber } from '@/lib/vat/vat-number'
+import { ACCOUNT_VAT_TREATMENTS } from '@/lib/vat/account-vat-treatment'
 import {
   accountNumberSchema,
   isoDateSchema,
@@ -2307,12 +2308,9 @@ const defaultVatRate = z
   .nullable()
   .optional()
 
-export const AccountVatTreatmentSchema = z.enum([
-  'standard_25', 'reduced_12', 'reduced_6', 'exempt',
-  'reverse_charge_domestic', 'reverse_charge_eu_goods',
-  'reverse_charge_eu_services', 'reverse_charge_non_eu_services',
-  'export_goods', 'export_services', 'vmb', 'rental_voluntary',
-])
+// Single source of truth for treatments is lib/vat/account-vat-treatment.ts;
+// the DB CHECK on chart_of_accounts.default_vat_treatment mirrors it per class.
+export const AccountVatTreatmentSchema = z.enum(ACCOUNT_VAT_TREATMENTS)
 
 const defaultVatTreatment = AccountVatTreatmentSchema.nullable().optional()
 

lib/import/__tests__/account-vat-treatment.test.ts

@@ -34,6 +34,29 @@ describe('enrichAccountMappingsWithVat', () => {
     })
   })
 
+  it('suggests oss from an OSS label and leaves the BAS 3106 label for review', () => {
+    const [oss, b2c] = enrichAccountMappingsWithVat(
+      [
+        mapping('3111', 'Försäljning enl. OSS (Spanien 21%)'),
+        mapping('3106', 'Försäljning varor till annat EU-land, momspliktig'),
+      ],
+      [],
+    )
+    expect(oss).toMatchObject({
+      defaultVatTreatment: 'oss',
+      defaultVatRate: null,
+      vatTreatmentSuggested: true,
+      vatTreatmentReviewed: false,
+      requiresVatTreatmentReview: true,
+    })
+    expect(b2c).toMatchObject({
+      defaultVatTreatment: null,
+      vatTreatmentSuggested: false,
+      vatTreatmentReviewed: false,
+      requiresVatTreatmentReview: true,
+    })
+  })
+
   it('keeps an existing account treatment without asking again', () => {
     const [result] = enrichAccountMappingsWithVat(
       [mapping('3041', 'Försäljning tjänst 25% sv')],

lib/reports/__tests__/vat-declaration.test.ts

@@ -1181,6 +1181,34 @@ describe('calculateVatDeclaration: company-specific ruta 05 accounts', () => {
     expect(result.breakdown.invoices.base25).toBe(2000)
   })
 
+  it('keeps accounts with the oss treatment out of every ruta, static 3001 included', async () => {
+    // Unionsordningen: the sale is declared in the quarterly OSS declaration
+    // and must not appear in the Swedish momsdeklaration at all. The explicit
+    // treatment also overrides the static BAS mapping of a 3001-style number.
+    chartAccounts = [
+      { account_number: '3001', default_vat_rate: null, default_vat_treatment: 'oss' },
+      {
+        account_number: '3106',
+        account_name: 'Försäljning enl. OSS (Tyskland 19%)',
+        default_vat_rate: null,
+        default_vat_treatment: 'oss',
+      },
+    ]
+    seedLedger([
+      { account_number: '3001', debit_amount: 0, credit_amount: 7000 },
+      { account_number: '3106', debit_amount: 0, credit_amount: 2000 },
+      { account_number: '2670', debit_amount: 0, credit_amount: 1710 },
+    ])
+
+    const result = await calculateVatDeclaration(supabase, 'company-1', 'monthly', 2024, 1)
+
+    expect(result.rutor.ruta05).toBe(0)
+    expect(result.rutor.ruta10).toBe(0)
+    expect(result.rutor.ruta35).toBe(0)
+    expect(result.rutor.ruta42).toBe(0)
+    expect(result.breakdown.invoices.base25).toBe(0)
+  })
+
   it('ignores missing rates without matching evidence and keeps explicit 0 % authoritative', async () => {
     // A number or a free-text label alone is not enough, and an explicit
     // "Ingen moms" always wins over the fallback convention.

lib/reports/vat-revenue-accounts.ts

@@ -15,7 +15,7 @@ export const RUTA_05_EXCLUDED_ACCOUNTS = new Set([
 const RUTA_05_STATIC_RATE_ACCOUNTS = new Set(['3000'])
 const DOMESTIC_SALES_RATE_BY_SUFFIX: Record<string, number> = { '1': 0.25, '2': 0.12, '3': 0.06 }
 const CONTRADICTING_ACCOUNT_NAME =
-  /momsfri|momsfritt|utan moms|omvänd|\bvmb\b|vinstmarginal|export|utanför|eu-land|unionsintern|\b0\s*%/i
+  /momsfri|momsfritt|utan moms|omvänd|\bvmb\b|vinstmarginal|export|utanför|eu-land|unionsintern|\boss\b|\b0\s*%/i
 
 function inferDomesticSalesRate(accountNumber: string, accountName: string): number | null {
   const accountMatch = /^30\d([123])$/.exec(accountNumber)

lib/vat/__tests__/account-vat-treatment.test.ts

@@ -3,6 +3,7 @@ import {
   defaultRateForVatTreatment,
   resolveVatTreatmentRuta,
   suggestVatTreatment,
+  vatTreatmentsForAccountClass,
 } from '../account-vat-treatment'
 
 describe('resolveVatTreatmentRuta', () => {
@@ -28,6 +29,16 @@ describe('resolveVatTreatmentRuta', () => {
     expect(resolveVatTreatmentRuta('export_goods', 4)).toBeNull()
     expect(resolveVatTreatmentRuta('exempt', 4)).toBeNull()
   })
+
+  it('keeps OSS revenue off the declaration and offers it only for revenue accounts', () => {
+    // Unionsordningen: declared in the OSS declaration, never in a ruta.
+    expect(resolveVatTreatmentRuta('oss', 3)).toBeNull()
+    expect(resolveVatTreatmentRuta('oss', 4)).toBeNull()
+    expect(vatTreatmentsForAccountClass(3)).toContain('oss')
+    expect(vatTreatmentsForAccountClass(3)).not.toContain('reverse_charge_non_eu_services')
+    expect(vatTreatmentsForAccountClass(4)).not.toContain('oss')
+    expect(defaultRateForVatTreatment('oss', 3)).toBeNull()
+  })
 })
 
 describe('suggestVatTreatment', () => {
@@ -61,6 +72,20 @@ describe('suggestVatTreatment', () => {
     })
   })
 
+  it('recognises OSS labels and leaves momspliktig EU-försäljning for review', () => {
+    // Fortnox has no OSS accounts in its base chart; users name their own
+    // per country and rate ("Försäljning enl. OSS (Spanien 21%)").
+    expect(suggestVatTreatment('3111', 'Försäljning enl. OSS (Spanien 21%)')).toEqual({
+      treatment: 'oss', rate: null,
+    })
+    expect(suggestVatTreatment('3112', 'Försäljning varor unionsordningen Tyskland')).toEqual({
+      treatment: 'oss', rate: null,
+    })
+    // BAS 3106 is Swedish moms below the OSS threshold or OSS above it; a
+    // ruta 35 (momsfri EU-leverans) suggestion is wrong either way.
+    expect(suggestVatTreatment('3106', 'Försäljning varor till annat EU-land, momspliktig')).toBeNull()
+  })
+
   it('does not match EU inside an unrelated word', () => {
     expect(suggestVatTreatment('4010', 'Reumatologiska varor')).toBeNull()
   })

lib/vat/account-vat-treatment.ts

@@ -5,6 +5,7 @@ export const ACCOUNT_VAT_TREATMENTS = [
   'reverse_charge_domestic', 'reverse_charge_eu_goods',
   'reverse_charge_eu_services', 'reverse_charge_non_eu_services',
   'export_goods', 'export_services', 'vmb', 'rental_voluntary',
+  'oss',
 ] as const
 
 export type AccountVatTreatment = typeof ACCOUNT_VAT_TREATMENTS[number]
@@ -15,13 +16,22 @@ export interface AccountVatRutaMapping {
   side: 'credit' | 'debit'
 }
 
-const REVENUE_RUTA: Record<AccountVatTreatment, keyof VatDeclarationRutor | null> = {
+/**
+ * Revenue (class 3) treatments and the momsdeklaration box they feed. A key
+ * mapped to `null` is a valid revenue treatment whose amounts are deliberately
+ * kept out of every ruta: OSS sales (unionsordningen) are declared only in the
+ * quarterly OSS declaration, never in the Swedish momsdeklaration
+ * (Skatteverket: "Den försäljning som du redovisar i OSS ska du inte redovisa
+ * i den vanliga momsdeklarationen"). Treatments missing from the map are
+ * purchase-only.
+ */
+const REVENUE_RUTA: Partial<Record<AccountVatTreatment, keyof VatDeclarationRutor | null>> = {
   standard_25: 'ruta05', reduced_12: 'ruta05', reduced_6: 'ruta05',
   exempt: 'ruta42', reverse_charge_domestic: 'ruta41',
   reverse_charge_eu_goods: 'ruta35', reverse_charge_eu_services: 'ruta39',
-  reverse_charge_non_eu_services: null,
   export_goods: 'ruta36', export_services: 'ruta40', vmb: 'ruta07',
   rental_voluntary: 'ruta08',
+  oss: null,
 }
 
 export function resolveVatTreatmentRuta(
@@ -48,6 +58,7 @@ export function isVatTreatmentAllowedForAccountClass(
   treatment: AccountVatTreatment,
   accountClass: number,
 ): boolean {
+  if (accountClass === 3) return treatment in REVENUE_RUTA
   return resolveVatTreatmentRuta(treatment, accountClass) !== null
 }
 
@@ -66,7 +77,9 @@ export function defaultRateForVatTreatment(
   if (treatment === 'reduced_12') return 0.12
   if (treatment === 'reduced_6') return 0.06
   if (treatment === 'exempt') return 0
-  if (treatment === 'vmb') return null
+  // VMB has no single sats; OSS accounts carry the destination country's
+  // rate, which is not a Swedish sats and never drives ruta 05 arithmetic.
+  if (treatment === 'vmb' || treatment === 'oss') return null
   if (treatment === 'rental_voluntary') return 0.25
   if (treatment === 'export_goods' || treatment === 'export_services') return 0
   return accountClass >= 4 && accountClass <= 6 ? 0.25 : 0
@@ -98,12 +111,20 @@ export function suggestVatTreatment(
   const rate = percent ? Number(percent[1]) / 100 : 0.25
 
   if (accountClass === 3) {
+    if (/\boss\b|one stop shop|unionsordning/.test(name)) return { treatment: 'oss', rate: null }
     if (/vmb|vinstmarginal/.test(name)) return { treatment: 'vmb', rate: null }
     if (/hyra|uthyrning/.test(name) && /frivillig/.test(name)) return { treatment: 'rental_voluntary', rate }
     if (/omvänd/.test(name)) return { treatment: 'reverse_charge_domestic', rate: 0 }
     if (/export|utanför eu/.test(name) && /var/.test(name)) return { treatment: 'export_goods', rate: 0 }
     if (/export|utanför eu/.test(name) && /tjänst|tjanst/.test(name)) return { treatment: 'export_services', rate: 0 }
-    if (/\beu\b/.test(name) && /var/.test(name)) return { treatment: 'reverse_charge_eu_goods', rate: 0 }
+    if (/\beu\b/.test(name) && /var/.test(name)) {
+      // BAS 3106 "Försäljning varor till annat EU-land, momspliktig" carries
+      // Swedish moms below the OSS threshold and destination-country moms
+      // (OSS) above it. The label cannot tell which, so leave the row for
+      // review instead of suggesting the momsfri ruta 35 treatment.
+      if (/momspliktig/.test(name)) return null
+      return { treatment: 'reverse_charge_eu_goods', rate: 0 }
+    }
     if (/\beu\b/.test(name) && /tjänst|tjanst/.test(name)) return { treatment: 'reverse_charge_eu_services', rate: 0 }
     if (/momsfri|utan moms/.test(name)) return { treatment: 'exempt', rate: 0 }
     if (/försälj|forsalj|intäkt|intakt/.test(name) && percent) {

messages/en.json

@@ -5312,6 +5312,7 @@
     "vat_treatment_export_services": "Services outside the EU",
     "vat_treatment_vmb": "Margin scheme (box 07)",
     "vat_treatment_rental_voluntary": "Voluntary VAT on rental income (box 08)",
+    "vat_treatment_oss": "OSS sales to EU consumers (reported in OSS, not on the VAT return)",
     "vat_rate_label": "VAT rate",
     "vat_rate_none": "None",
     "vat_review_confirm_all": "Confirm all suggested ({count})",

messages/sv.json

@@ -5312,6 +5312,7 @@
     "vat_treatment_export_services": "Tjänster utanför EU",
     "vat_treatment_vmb": "Vinstmarginalbeskattning (ruta 07)",
     "vat_treatment_rental_voluntary": "Frivillig moms på uthyrning (ruta 08)",
+    "vat_treatment_oss": "OSS-försäljning till EU-konsumenter (redovisas i OSS, inte i momsdeklarationen)",
     "vat_rate_label": "Momssats",
     "vat_rate_none": "Ingen",
     "vat_review_confirm_all": "Bekräfta alla föreslagna ({count})",

supabase/migrations/20260822093000_account_vat_treatment_oss.sql

@@ -0,0 +1,38 @@
+-- OSS (unionsordningen): sales to EU consumers above the EUR 10 000 threshold
+-- carry the destination country's VAT and are declared only in the quarterly
+-- OSS declaration, never in the Swedish momsdeklaration. The 'oss' revenue
+-- treatment keeps such accounts out of every ruta; the resolver lives in
+-- lib/vat/account-vat-treatment.ts. Purchase classes are unchanged.
+ALTER TABLE public.chart_of_accounts
+  DROP CONSTRAINT IF EXISTS chart_of_accounts_default_vat_treatment_check;
+
+ALTER TABLE public.chart_of_accounts
+  ADD CONSTRAINT chart_of_accounts_default_vat_treatment_check
+  CHECK (
+    default_vat_treatment IS NULL
+    OR (
+      account_class = 3
+      AND default_vat_treatment IN (
+        'standard_25', 'reduced_12', 'reduced_6', 'exempt',
+        'reverse_charge_domestic', 'reverse_charge_eu_goods',
+        'reverse_charge_eu_services', 'export_goods', 'export_services',
+        'vmb', 'rental_voluntary', 'oss'
+      )
+    )
+    OR (
+      account_class BETWEEN 4 AND 6
+      AND default_vat_treatment IN (
+        'reverse_charge_domestic', 'reverse_charge_eu_goods',
+        'reverse_charge_eu_services', 'reverse_charge_non_eu_services'
+      )
+    )
+  ) NOT VALID;
+
+-- Superset of the previous constraint: validation cannot fail on existing rows.
+ALTER TABLE public.chart_of_accounts
+  VALIDATE CONSTRAINT chart_of_accounts_default_vat_treatment_check;
+
+COMMENT ON COLUMN public.chart_of_accounts.default_vat_treatment IS
+  'Per-account momsdeklaration treatment. Explicit values override the built-in BAS account mapping; ''oss'' keeps revenue out of the Swedish declaration (declared in OSS).';
+
+NOTIFY pgrst, 'reload schema';

supabase/migrations/__tests__/account-default-vat-treatment.pg.test.ts

@@ -63,7 +63,7 @@ describe('chart_of_accounts.default_vat_treatment', () => {
       'standard_25', 'reduced_12', 'reduced_6', 'exempt',
       'reverse_charge_domestic', 'reverse_charge_eu_goods',
       'reverse_charge_eu_services', 'export_goods', 'export_services',
-      'vmb', 'rental_voluntary', null,
+      'vmb', 'rental_voluntary', 'oss', null,
     ]
     for (const treatment of revenueTreatments) {
       await expect(setTreatment(companyId, '3001', treatment)).resolves.toBeDefined()
@@ -89,6 +89,14 @@ describe('chart_of_accounts.default_vat_treatment', () => {
     await expect(setTreatment(companyId, '4010', 'standard_25')).rejects.toThrow()
   })
 
+  it('accepts oss only on revenue accounts (20260822093000_account_vat_treatment_oss)', async () => {
+    const { companyId, userId } = await seedCompany()
+    await insertAccount(companyId, userId, '3106', 3)
+    await insertAccount(companyId, userId, '4010', 4)
+    await expect(setTreatment(companyId, '3106', 'oss')).resolves.toBeDefined()
+    await expect(setTreatment(companyId, '4010', 'oss')).rejects.toThrow()
+  })
+
   it('normalizes values accepted by the predecessor before enforcing classes', async () => {
     const { companyId, userId } = await seedCompany()
     await insertAccount(companyId, userId, '1010', 1)