diff --git a/DECISIONS.md b/DECISIONS.md
index 150ef327..664b9fcb 100644
--- a/DECISIONS.md
+++ b/DECISIONS.md
@@ -1151,6 +1151,7 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-21] RIP-4 cascade step 3 (UI): the AI booking proposal is surfaced INSIDE the existing QuickReviewDialog rather than a new inline-row card, so it reuses that dialog's proven, deterministic, balanced commit path (POST /api/transactions/[id]/categorize) instead of a parallel one. components/transactions/AiCategorizeProposal.tsx fetches POST /api/agent/categorize on dialog open (keyed on tx.id so it remounts per transaction), pre-fills accountOverride + vatTreatment via handleAccountChange (class-2 VAT clearing preserved), and shows the confidence band (säker/trolig/välj konto) + "Varför" + the candidate alternatives (click to re-apply). Falls back SILENTLY to the deterministic defaults on error, and shows a soft note on 503 (ai_unconfigured) — the dialog always works without AI. NO silent auto-posting (founder call, avoids the storno-on-undo mess): "säker" = pre-filled, one-tap Bokför via the dialog's existing button; true hands-off auto-book waits for calibration. i18n: strings inline Swedish for now (assistant surface), lift to messages/{sv,en}.json before final merge. Confidence bands (0.8/0.5) are placeholders until calibration. Needs founder visual sign-off before merge ([[project_nav_ia_redesign]]).
 [2026-08-21] RIP-4 step 4 = calibration. lib/agent/categorize/calibration.ts is the engine: isotonic regression via pool-adjacent-violators (distribution-free, monotonic) over (confidence, was_correct) samples → a calibrator that turns raw selector confidence into a probability that actually means what it says; plus reliabilityByBucket/ECE and bandFor(). bandFor NEVER returns 'auto' without a fitted calibrator (no silent booking on an unproven score) and never auto-books above an amount cap (default 2000 kr) — so "säker" stays honest until proven. Measurement loop: migration 20260821100000 categorize_calibration_samples (append-only, company-scoped RLS, confidence CHECK [0,1]); POST /api/agent/categorize/outcome logs one sample (proposed vs booked account → was_correct) fire-and-forget from QuickReviewDialog on a successful book (sandbox skipped to keep the corpus clean); AiCategorizeProposal surfaces the proposal metadata via onProposal. scripts/fit-categorize-calibration.ts (READ-ONLY) prints the reliability diagram + ECE + fitted calibrator once data exists — run it in a few weeks, then store the calibrator/thresholds where bandFor reads them and only THEN consider enabling auto-book. Fitting needs >=200 real samples so nothing calibrates today; the loop just starts collecting. Migration applies on merge (auto-apply-on-merge active) — not applied manually.
 [2026-08-21] The categorize selector now reads the underlag, not just the bank line — the highest-leverage quality lever for the cold-start majority (prod: 365 companies with 32.7k unbooked tx, median 0 templates, so the LLM carries them). lib/agent/categorize/underlag.ts gathers the matched receipt/invoice text (receipts.matched_transaction_id + invoice_inbox_items.matched_transaction_id + the transaction's own document_attachments), rendered as bounded Swedish text (supplier, date, total, moms, line items). Core reads these tables directly via supabase (table names, not @/extensions imports — the tables live in the shared DB). POST /api/agent/categorize gathers it server-side when the caller didn't pass `underlag`, so the model sees the actual supplier + line items. Best-effort ('' on any failure); server-side only, no client change (so no conflict with the calibration PR #1784 which also touches the dialog). Prod read (project pwxtzglxptnnvjrpixpg) also confirmed: 3342 active counterparty templates / 26k occurrences → established users get strong instant candidates; NO backfill needed (templates already reflect historical bookings).
+[2026-08-21] A personnummer-shaped org_number on customer_type=individual is MOVED into personal_number (encrypted, masked on read) and org_number cleared, on every write path (CreateCustomerSchema transform for web/v1/bulk, both PATCH routes, MCP gnubok_create_customer at staging and commitCreateCustomer for in-flight ops), rather than rejected like the business-type case (#1724): the value is unambiguously the person's own personnummer, the MCP tool had no personal_number input until now so agents had nowhere else to put it (134 such rows across 10 companies on prod), and the v1 docs promised org_number was accepted for individuals, so a 400 would break live clients for no privacy gain. Only an org_number that is a DIFFERENT personnummer than a submitted personal_number is refused (CUSTOMER_PERSONAL_NUMBER_CONFLICT). MCP stages the personnummer encrypted (personal_number_encrypted + personal_number_masked, personal_number is now a forbidden staging key) and hashes the masked preview for idempotency, since the random-IV ciphertext would make identical retries look like payload changes. Read surfaces (web customer list, MCP list_customers) mask a legacy individual row's org_number personnummer instead of showing it raw; scripts/repair-customer-personal-number-in-org-number.ts moves the existing rows and is run by hand with --confirm after deploy. MCP create_customer payment_terms are resolved from company_settings at staging: the staging-side || 30 is why #1708's fix never reached MCP customers.
 [2026-08-21] Peppol receiving (PR2) keeps Qvalia's consolidated partner account: every company's 0007:orgnr is registered on OUR account (PUT /partner/{p}/account/{p}/peppol/{id}) and inbound documents are routed by the AccountingCustomerParty EndpointID through peppol_registrations, because Qvalia confirmed sending needs no per-company account and child accounts would only add a 100 kr/mån tenant fee per customer; the exact received UBL XML is archived as a WORM document (upload_source e_invoice, extractionOwner none) and the inbox row is filled from the structured UBL with confidence 1 (no model pass), following the mail-hunt precedent of core inserting invoice_inbox_items directly; personnummer-based companies are refused registration until 0088 GLN support exists (publishing them would put personal data in the Peppol Directory); the poll is a 10-minute cron (GET .../readinvoices marks documents read at Qvalia, so every fetched document is archived before anything else can fail).
 [2026-08-21] Confidence honesty fix, driven by a real backtest (scripts/backtest-categorize.ts, read-only: runs the real cascade on already-booked prod transactions and scores the model's pick vs the human's actual account). Backtest exposed the selector reporting 0.95 on pure category guesses → "säker" was a lie (high-conf picks only 52% accurate). Fix: confidence is now driven by DETERMINISTIC BACKING (the confidence of a candidate that independently points at the chosen account), not the model's verbalized confidence (which the backtest showed is ~always "high"). A backed pick takes the candidate confidence, reduced only when the model is unsure (BACKED_MODEL_FACTOR); an UNBACKED pick (category guess no candidate agreed with) is capped at 0.7 — below the säker band (0.8) — so a guess is never "säker". Re-backtest: säker accuracy 52% → 73%, and far fewer picks claim säker (only template-backed ones). Still not auto-book-grade (~73%, want ~95%); auto-book stays off until isotonic calibration on real approvals. Backtest caveats: exact-account match is strict (penalizes reasonable-but-different picks + companies' idiosyncratic charts), sample is established users (cold-start majority has no ground truth yet), backtest ran samples=1 (no self-consistency). Some confident-wrong cases are POISONED templates (a past mis-booking → wrong candidate the model correctly follows), a data-quality issue not fixable in the confidence math.
 [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.
diff --git a/app/(dashboard)/customers/page.tsx b/app/(dashboard)/customers/page.tsx
index f2feecb6..612cde86 100644
--- a/app/(dashboard)/customers/page.tsx
+++ b/app/(dashboard)/customers/page.tsx
@@ -19,6 +19,7 @@ import { cn } from '@/lib/utils'
 import Link from 'next/link'
 import { useCanWrite } from '@/lib/hooks/use-can-write'
 import type { Customer, CustomerType, CreateCustomerInput } from '@/types'
+import { customerListIdentifier } from '@/lib/customers/mask-personal-number'
 
 const CustomerForm = dynamic(
   () => import('@/components/customers/CustomerForm'),
@@ -53,8 +54,11 @@ const SORTABLE_COLUMNS: ReadonlyArray<SortColumn> = [
 ]
 const INITIAL_VISIBLE_ROWS = 100
 
+// Business rows show org_number; individual rows show the masked
+// personnummer the API returns, and a legacy individual row that still
+// carries its personnummer in org_number shows that masked too, never raw.
 function getIdentifier(customer: Customer): string {
-  return customer.org_number || customer.personal_number || ''
+  return customerListIdentifier(customer)
 }
 
 function compareStrings(a: string, b: string): number {
diff --git a/app/api/customers/[id]/route.ts b/app/api/customers/[id]/route.ts
index e576c323..49e2f7fa 100644
--- a/app/api/customers/[id]/route.ts
+++ b/app/api/customers/[id]/route.ts
@@ -5,7 +5,12 @@ import { validateVatNumber } from '@/lib/vat/vies-client'
 import { withRouteContext } from '@/lib/api/with-route-context'
 import { errorResponseFromCode } from '@/lib/errors/get-structured-error'
 import { encryptCustomerPersonalNumber, maskCustomerRow } from '@/lib/customers/protect-personal-number'
-import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+  personalNumberDigits,
+} from '@/lib/customers/personal-number-shape'
 import { isMaskedPersonalNumber } from '@/lib/customers/mask-personal-number'
 import { getErrorMessage as getUserErrorMessage } from '@/lib/errors/get-error-message'
 
@@ -107,6 +112,23 @@ export const PATCH = withRouteContext(
       return errorResponseFromCode('CUSTOMER_ORG_NUMBER_IS_PERSONAL', opLog, { requestId })
     }
 
+    // The mirror image for individuals: a personnummer submitted as
+    // org_number is the personnummer in the wrong field. It is stored
+    // encrypted in personal_number and org_number is cleared, same as
+    // CreateCustomerSchema does on create. Next to a DIFFERENT plaintext
+    // personal_number in the same body the two conflict.
+    const reroutedPersonalNumber = orgNumberHoldsPersonalNumber(effectiveType, body.org_number)
+      ? normalizeReroutedPersonalNumber(body.org_number!)
+      : null
+    if (
+      reroutedPersonalNumber
+      && personalNumberSubmitted
+      && body.personal_number
+      && personalNumberDigits(body.personal_number) !== personalNumberDigits(reroutedPersonalNumber)
+    ) {
+      return errorResponseFromCode('CUSTOMER_PERSONAL_NUMBER_CONFLICT', opLog, { requestId })
+    }
+
     const updateData: Record<string, unknown> = {}
     if (body.name !== undefined) updateData.name = body.name
     if (body.customer_type !== undefined) updateData.customer_type = body.customer_type
@@ -126,9 +148,13 @@ export const PATCH = withRouteContext(
     if (body.postal_code !== undefined) updateData.postal_code = body.postal_code
     if (body.city !== undefined) updateData.city = body.city
     if (body.country !== undefined) updateData.country = body.country
-    if (body.org_number !== undefined) updateData.org_number = body.org_number
+    if (body.org_number !== undefined) {
+      updateData.org_number = reroutedPersonalNumber ? null : body.org_number
+    }
     if (body.vat_number !== undefined) updateData.vat_number = body.vat_number
-    if (personalNumberSubmitted) {
+    if (reroutedPersonalNumber && !(personalNumberSubmitted && body.personal_number)) {
+      updateData.personal_number = encryptCustomerPersonalNumber(reroutedPersonalNumber)
+    } else if (personalNumberSubmitted) {
       // Stored as ciphertext; customers_personal_number_check accepts that
       // shape only (20260726110000).
       updateData.personal_number = encryptCustomerPersonalNumber(body.personal_number)
diff --git a/app/api/customers/__tests__/personal-number.test.ts b/app/api/customers/__tests__/personal-number.test.ts
index 98c67193..4227f914 100644
--- a/app/api/customers/__tests__/personal-number.test.ts
+++ b/app/api/customers/__tests__/personal-number.test.ts
@@ -405,3 +405,97 @@ describe('personal_number on customer routes', () => {
     expect(response.status).toBe(404)
   })
 })
+
+// A personnummer submitted as org_number on an individual is the personnummer
+// in the wrong field: stored encrypted in personal_number, org_number left
+// empty, on create and on update alike.
+describe('personnummer submitted as org_number on an individual', () => {
+  const routeParams = { params: Promise.resolve({ id: 'customer-1' }) }
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    eventBus.clear()
+    captured.insert.length = 0
+    captured.update.length = 0
+    queryResult = { data: null, error: null }
+    requireAuthMock.mockResolvedValue({ user: { id: 'user-1' }, supabase })
+    requireWriteMock.mockResolvedValue({ ok: true })
+  })
+
+  it('POST stores it encrypted as personal_number and leaves org_number empty', async () => {
+    queryResult = {
+      data: {
+        id: 'customer-1',
+        name: 'Bertil Bengtsson',
+        customer_type: 'individual',
+        org_number: null,
+        personal_number: encryptPersonnummer(PERSONAL_NUMBER),
+      },
+      error: null,
+    }
+
+    const response = await POST(
+      createMockRequest('/api/customers', {
+        method: 'POST',
+        body: { name: 'Bertil Bengtsson', customer_type: 'individual', org_number: PERSONAL_NUMBER },
+      }),
+      { params: Promise.resolve({}) },
+    )
+
+    const { status, body } = await parseJsonResponse<{ data: { personal_number: string; org_number: string | null } }>(response)
+    expect(status).toBe(200)
+    const inserted = captured.insert[0] as { org_number?: string | null; personal_number?: string | null }
+    expect(inserted.org_number ?? null).toBeNull()
+    expect(inserted.personal_number).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(inserted.personal_number!)).toBe(PERSONAL_NUMBER)
+    expect(JSON.stringify(inserted)).not.toContain(PERSONAL_NUMBER)
+    expect(body.data.personal_number).toBe(MASKED)
+  })
+
+  it('PATCH stores it encrypted as personal_number and clears org_number', async () => {
+    queryResult = {
+      data: {
+        id: 'customer-1',
+        customer_type: 'individual',
+        org_number: null,
+        personal_number: encryptPersonnummer(PERSONAL_NUMBER),
+      },
+      error: null,
+    }
+
+    const response = await PATCH(
+      createMockRequest('/api/customers/customer-1', {
+        method: 'PATCH',
+        body: { org_number: PERSONAL_NUMBER },
+      }),
+      routeParams,
+    )
+
+    const { status } = await parseJsonResponse<unknown>(response)
+    expect(status).toBe(200)
+    const updated = captured.update[0] as { org_number?: string | null; personal_number?: string | null }
+    expect(updated.org_number).toBeNull()
+    expect(updated.personal_number).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(updated.personal_number!)).toBe(PERSONAL_NUMBER)
+  })
+
+  it('PATCH refuses an org_number that is a different personnummer than personal_number', async () => {
+    queryResult = {
+      data: { id: 'customer-1', customer_type: 'individual' },
+      error: null,
+    }
+
+    const response = await PATCH(
+      createMockRequest('/api/customers/customer-1', {
+        method: 'PATCH',
+        body: { org_number: '19850505-5555', personal_number: PERSONAL_NUMBER },
+      }),
+      routeParams,
+    )
+
+    const { status, body } = await parseJsonResponse<unknown>(response)
+    expect(status).toBe(400)
+    expect(JSON.stringify(body)).toContain('CUSTOMER_PERSONAL_NUMBER_CONFLICT')
+    expect(captured.update).toHaveLength(0)
+  })
+})
diff --git a/app/api/v1/companies/[companyId]/customers/[id]/route.ts b/app/api/v1/companies/[companyId]/customers/[id]/route.ts
index 3f3919ea..72faa962 100644
--- a/app/api/v1/companies/[companyId]/customers/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/customers/[id]/route.ts
@@ -26,7 +26,12 @@ import {
   maskCustomerRow,
 } from '@/lib/customers/protect-personal-number'
 import { isMaskedPersonalNumber } from '@/lib/customers/mask-personal-number'
-import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+  personalNumberDigits,
+} from '@/lib/customers/personal-number-shape'
 
 // v1-only extension: allow PATCH to set archived_at back to null to
 // un-archive a customer. Restricted to literal `null` so the caller can't
@@ -242,7 +247,7 @@ registerEndpoint({
     'org_number uniqueness is enforced at DB level: 23505 → 409 CUSTOMER_DUPLICATE_ORG_NUMBER.',
     'VIES re-validation is best-effort and runs only on commit. A VIES timeout does not fail the update.',
     'personal_number: a plaintext value is stored encrypted (individual customers only); the masked form a read returned (********-1234) means "leave unchanged" and is never stored; null clears it. Changing customer_type away from individual clears any stored personal_number.',
-    'An org_number shaped like a Swedish personnummer is rejected for business customer_types (400 CUSTOMER_ORG_NUMBER_IS_PERSONAL).',
+    'An org_number shaped like a Swedish personnummer is rejected for business customer_types (400 CUSTOMER_ORG_NUMBER_IS_PERSONAL). On an individual it is the personnummer in the wrong field: it is stored encrypted as personal_number and org_number is cleared; next to a different personal_number in the same body it is 400 CUSTOMER_PERSONAL_NUMBER_CONFLICT.',
   ],
   example: {
     request: { default_payment_terms: 14, notes: 'New payment terms agreed 2026-05-12.' },
@@ -350,6 +355,26 @@ export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string
       })
     }
 
+    // The mirror image for individuals: a personnummer submitted as
+    // org_number is the personnummer in the wrong field. It is stored
+    // encrypted in personal_number and org_number is cleared, same as
+    // CreateCustomerSchema does on create. Next to a DIFFERENT plaintext
+    // personal_number in the same body the two conflict.
+    const reroutedPersonalNumber = orgNumberHoldsPersonalNumber(effectiveType, body.org_number)
+      ? normalizeReroutedPersonalNumber(body.org_number!)
+      : null
+    if (
+      reroutedPersonalNumber
+      && personalNumberSubmitted
+      && body.personal_number
+      && personalNumberDigits(body.personal_number) !== personalNumberDigits(reroutedPersonalNumber)
+    ) {
+      return v1ErrorResponseFromCode('CUSTOMER_PERSONAL_NUMBER_CONFLICT', ctx.log, {
+        requestId: ctx.requestId,
+        details: { field: 'org_number' },
+      })
+    }
+
     // Build the partial update set. Fields explicitly set to undefined in
     // the body are not in the resulting object (Zod strips undefined). null
     // IS allowed and means "clear the field" (or, for archived_at, "un-archive").
@@ -381,7 +406,10 @@ export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string
     if (body.customer_number !== undefined) {
       updateData.customer_number = body.customer_number || null
     }
-    if (personalNumberSubmitted) {
+    if (reroutedPersonalNumber) updateData.org_number = null
+    if (reroutedPersonalNumber && !(personalNumberSubmitted && body.personal_number)) {
+      updateData.personal_number = encryptCustomerPersonalNumber(reroutedPersonalNumber)
+    } else if (personalNumberSubmitted) {
       // Stored as ciphertext; customers_personal_number_check accepts that
       // shape only (20260726110000).
       updateData.personal_number = encryptCustomerPersonalNumber(body.personal_number)
diff --git a/app/api/v1/companies/[companyId]/customers/__tests__/route.test.ts b/app/api/v1/companies/[companyId]/customers/__tests__/route.test.ts
index 8e53a497..569496cf 100644
--- a/app/api/v1/companies/[companyId]/customers/__tests__/route.test.ts
+++ b/app/api/v1/companies/[companyId]/customers/__tests__/route.test.ts
@@ -1180,3 +1180,96 @@ describe('company payment-terms default on create', () => {
     expect(supabaseMock.from.mock.calls.some((c) => c[0] === 'customers')).toBe(false)
   })
 })
+
+// A personnummer submitted as org_number on an individual is the personnummer
+// in the wrong field: stored encrypted in personal_number, org_number left
+// empty, on create and on update alike. (The pre-2026-08-21 docs told callers
+// org_number was accepted for individuals; it still is, it just lands right.)
+describe('personnummer submitted as org_number on an individual (v1)', () => {
+  it('POST stores it encrypted as personal_number and returns org_number empty', async () => {
+    withWriteScope()
+    const supabaseMock = makeFlexibleSupabase({
+      company_members: { data: { company_id: COMPANY_ID, role: 'owner' }, error: null },
+      customers: {
+        data: {
+          ...SAMPLE_CUSTOMER,
+          customer_type: 'individual',
+          org_number: null,
+          vat_number: null,
+          personal_number: TEST_PERSONAL_NUMBER,
+        },
+        error: null,
+      },
+    })
+    mockServiceClient.mockReturnValue(supabaseMock)
+
+    const res = await createCustomer(
+      makePostRequest(`https://x.test/api/v1/companies/${COMPANY_ID}/customers`, {
+        name: 'Bertil Bengtsson',
+        customer_type: 'individual',
+        org_number: TEST_PERSONAL_NUMBER,
+      }),
+      companyParams(COMPANY_ID),
+    )
+
+    expect(res.status).toBe(201)
+    const inserted = supabaseMock.captured.insert[0] as { org_number?: string | null; personal_number?: string | null }
+    expect(inserted.org_number ?? null).toBeNull()
+    expect(inserted.personal_number).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(inserted.personal_number!)).toBe(TEST_PERSONAL_NUMBER)
+    expect(JSON.stringify(inserted)).not.toContain(TEST_PERSONAL_NUMBER)
+    const body = await res.json()
+    expect(body.data.personal_number).toBe(MASKED_PERSONAL_NUMBER)
+    expect(body.data.org_number).toBeNull()
+  })
+
+  it('PATCH stores it encrypted as personal_number and clears org_number', async () => {
+    withWriteScope()
+    const supabaseMock = makeFlexibleSupabase({
+      company_members: { data: { company_id: COMPANY_ID, role: 'owner' }, error: null },
+      customers: {
+        data: { ...SAMPLE_CUSTOMER, customer_type: 'individual', org_number: null, personal_number: TEST_PERSONAL_NUMBER },
+        error: null,
+      },
+    })
+    mockServiceClient.mockReturnValue(supabaseMock)
+
+    const res = await updateCustomer(
+      makePatchRequest(`https://x.test/api/v1/companies/${COMPANY_ID}/customers/${CUSTOMER_ID}`, {
+        org_number: TEST_PERSONAL_NUMBER,
+      }),
+      detailParams(COMPANY_ID, CUSTOMER_ID),
+    )
+
+    expect(res.status).toBe(200)
+    const updated = supabaseMock.captured.update[0] as { org_number?: string | null; personal_number?: string | null }
+    expect(updated.org_number).toBeNull()
+    expect(updated.personal_number).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(updated.personal_number!)).toBe(TEST_PERSONAL_NUMBER)
+  })
+
+  it('PATCH refuses an org_number that is a different personnummer than personal_number', async () => {
+    withWriteScope()
+    const supabaseMock = makeFlexibleSupabase({
+      company_members: { data: { company_id: COMPANY_ID, role: 'owner' }, error: null },
+      customers: {
+        data: { ...SAMPLE_CUSTOMER, customer_type: 'individual' },
+        error: null,
+      },
+    })
+    mockServiceClient.mockReturnValue(supabaseMock)
+
+    const res = await updateCustomer(
+      makePatchRequest(`https://x.test/api/v1/companies/${COMPANY_ID}/customers/${CUSTOMER_ID}`, {
+        org_number: '19850505-5555',
+        personal_number: TEST_PERSONAL_NUMBER,
+      }),
+      detailParams(COMPANY_ID, CUSTOMER_ID),
+    )
+
+    expect(res.status).toBe(400)
+    const body = await res.json()
+    expect(body.error.code).toBe('CUSTOMER_PERSONAL_NUMBER_CONFLICT')
+    expect(supabaseMock.captured.update).toHaveLength(0)
+  })
+})
diff --git a/app/api/v1/companies/[companyId]/customers/route.ts b/app/api/v1/companies/[companyId]/customers/route.ts
index ba6b9b20..422ad8f9 100644
--- a/app/api/v1/companies/[companyId]/customers/route.ts
+++ b/app/api/v1/companies/[companyId]/customers/route.ts
@@ -280,8 +280,8 @@ registerEndpoint({
   pitfalls: [
     'Idempotency-Key is mandatory: calls without it return 400 VALIDATION_ERROR.',
     'org_number uniqueness is enforced at the database level; duplicate inserts return 409 CUSTOMER_DUPLICATE_ORG_NUMBER.',
-    'For Swedish sole traders (customer_type=individual), org_number IS the personnummer. List responses mask it; the create endpoint accepts it as input.',
-    'An org_number shaped like a Swedish personnummer is rejected for business customer_types: create the customer as customer_type=individual (personal_number or org_number) so the number is masked and protected.',
+    'A personnummer-shaped org_number on customer_type=individual is treated as the personnummer submitted in the wrong field: it is stored encrypted as personal_number, returned masked (********-1234), and org_number is left empty. Prefer passing it as personal_number. Next to a different personal_number in the same body it is a 400.',
+    'An org_number shaped like a Swedish personnummer is rejected for business customer_types: create the customer as customer_type=individual with personal_number so the number is masked and protected.',
     'personal_number is accepted only for customer_type=individual, stored encrypted, and returned in the masked form ********-1234.',
     'If default_payment_terms is omitted, it defaults to the company setting invoice_default_days, falling back to 30.',
     'VIES validation runs only on commit. Dry-run skips the external call and leaves vat_number_validated=false in the preview.',
diff --git a/components/pending-operations/OperationPreview.tsx b/components/pending-operations/OperationPreview.tsx
index 2cdfd16c..77f0c378 100644
--- a/components/pending-operations/OperationPreview.tsx
+++ b/components/pending-operations/OperationPreview.tsx
@@ -174,6 +174,12 @@ function CustomerPreview({ data }: { data: Record<string, unknown> }) {
           <span className="font-mono">{String(data.org_number)}</span>
         </>
       ) : null}
+      {data.personal_number_masked ? (
+        <>
+          <span className="text-muted-foreground">Personnr</span>
+          <span className="font-mono">{String(data.personal_number_masked)}</span>
+        </>
+      ) : null}
     </div>
   )
 }
diff --git a/extensions/general/mcp-server/__tests__/create-customer.test.ts b/extensions/general/mcp-server/__tests__/create-customer.test.ts
index ba2ceb5c..9909c0b3 100644
--- a/extensions/general/mcp-server/__tests__/create-customer.test.ts
+++ b/extensions/general/mcp-server/__tests__/create-customer.test.ts
@@ -1,6 +1,8 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { createQueuedMockSupabase } from '@/tests/helpers'
 import { eventBus } from '@/lib/events/bus'
+import { hashRequest } from '@/lib/api/idempotency'
+import { decryptPersonnummer } from '@/lib/salary/personnummer'
 import { tools } from '../server'
 
 const tool = () => tools.find((candidate) => candidate.name === 'gnubok_create_customer')!
@@ -19,6 +21,7 @@ describe('gnubok_create_customer: customer_number input', () => {
 
   it('stages the trimmed customer_number in params and preview', async () => {
     const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null }) // company_settings read (payment-terms default)
     enqueue({ data: { id: 'op-create-customer-1' } })
 
     const result = (await tool().execute(
@@ -76,6 +79,7 @@ describe('gnubok_create_customer: customer_number input', () => {
 
   it('stages customer_number as null when omitted', async () => {
     const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null }) // company_settings read (payment-terms default)
     enqueue({ data: { id: 'op-create-customer-2' } })
 
     const result = (await tool().execute(
@@ -94,3 +98,270 @@ describe('gnubok_create_customer: customer_number input', () => {
     expect(inserted.params).toMatchObject({ customer_number: null })
   })
 })
+
+// ── personal_number (privatperson) ────────────────────────────────────
+//
+// Synthetic personnummer, never a real one. Ciphertext shape enforced by
+// customers_personal_number_check (20260726110000).
+const PERSONAL_NUMBER = '19900101-1234'
+const MASKED = '********-1234'
+const CIPHERTEXT_SHAPE = /^[0-9a-f]{76,255}$/
+
+type StagedInsert = {
+  title: string
+  params: Record<string, unknown>
+  preview_data: Record<string, unknown>
+}
+
+describe('gnubok_create_customer: personal_number', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    eventBus.clear()
+  })
+
+  it('exposes personal_number in the strict input schema', () => {
+    const properties = tool().inputSchema.properties as Record<string, Record<string, unknown>>
+    expect(properties.personal_number).toMatchObject({ type: 'string' })
+  })
+
+  it('stages the personnummer encrypted and previews it masked, never in plaintext', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null }) // company_settings read (payment-terms default)
+    enqueue({ data: { id: 'op-pn-1' } }) // pending_operations insert
+
+    const result = (await tool().execute(
+      { name: 'Anna Andersson', customer_type: 'individual', personal_number: PERSONAL_NUMBER },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { staged: boolean; preview: Record<string, unknown> }
+
+    expect(result.staged).toBe(true)
+    expect(result.preview.personal_number_masked).toBe(MASKED)
+    expect(result.preview).not.toHaveProperty('personal_number')
+    expect(result.preview).not.toHaveProperty('personal_number_encrypted')
+    expect(JSON.stringify(result)).not.toContain(PERSONAL_NUMBER)
+
+    const inserted = findCall('pending_operations', 'insert')?.[0] as StagedInsert
+    expect(inserted.params.personal_number_encrypted).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(inserted.params.personal_number_encrypted as string)).toBe(PERSONAL_NUMBER)
+    expect(inserted.params).not.toHaveProperty('personal_number')
+    expect(inserted.preview_data.personal_number_masked).toBe(MASKED)
+    // Nothing persisted carries the plaintext: not params, not preview, not title.
+    expect(JSON.stringify(inserted)).not.toContain(PERSONAL_NUMBER)
+  })
+
+  it('moves a personnummer-shaped org_number on an individual into personal_number', async () => {
+    // What every agent had to do before this tool had a personal_number input.
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null })
+    enqueue({ data: { id: 'op-pn-2' } })
+
+    const result = (await tool().execute(
+      { name: 'Bertil Bengtsson', customer_type: 'individual', org_number: PERSONAL_NUMBER },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { staged: boolean; preview: Record<string, unknown> }
+
+    expect(result.preview.org_number).toBeNull()
+    expect(result.preview.personal_number_masked).toBe(MASKED)
+
+    const inserted = findCall('pending_operations', 'insert')?.[0] as StagedInsert
+    expect(inserted.params.org_number).toBeNull()
+    expect(decryptPersonnummer(inserted.params.personal_number_encrypted as string)).toBe(PERSONAL_NUMBER)
+    expect(JSON.stringify(inserted)).not.toContain(PERSONAL_NUMBER)
+  })
+
+  it('refuses a personnummer-shaped org_number on a business customer before staging', async () => {
+    const { supabase } = createQueuedMockSupabase()
+
+    await expect(
+      tool().execute(
+        { name: 'Enskild Firma X', customer_type: 'swedish_business', org_number: PERSONAL_NUMBER },
+        'company-1',
+        'user-1',
+        supabase as never,
+      ),
+    ).rejects.toThrow(/personnummer/)
+    expect(supabase.from).not.toHaveBeenCalled()
+  })
+
+  it('refuses personal_number on a business customer', async () => {
+    const { supabase } = createQueuedMockSupabase()
+
+    await expect(
+      tool().execute(
+        { name: 'Kund AB', customer_type: 'swedish_business', personal_number: PERSONAL_NUMBER },
+        'company-1',
+        'user-1',
+        supabase as never,
+      ),
+    ).rejects.toThrow(/individual/)
+    expect(supabase.from).not.toHaveBeenCalled()
+  })
+
+  it('refuses a malformed personal_number', async () => {
+    const { supabase } = createQueuedMockSupabase()
+
+    await expect(
+      tool().execute(
+        { name: 'Anna Andersson', customer_type: 'individual', personal_number: 'not-a-personnummer' },
+        'company-1',
+        'user-1',
+        supabase as never,
+      ),
+    ).rejects.toThrow(/personnummer/)
+    expect(supabase.from).not.toHaveBeenCalled()
+  })
+
+  it('refuses an org_number that is a different personnummer than personal_number', async () => {
+    const { supabase } = createQueuedMockSupabase()
+
+    await expect(
+      tool().execute(
+        {
+          name: 'Anna Andersson',
+          customer_type: 'individual',
+          org_number: '19850505-5555',
+          personal_number: PERSONAL_NUMBER,
+        },
+        'company-1',
+        'user-1',
+        supabase as never,
+      ),
+    ).rejects.toThrow(/differs/)
+    expect(supabase.from).not.toHaveBeenCalled()
+  })
+
+  it('dry_run returns the masked preview without staging', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null }) // company_settings read
+
+    const result = (await tool().execute(
+      { name: 'Anna Andersson', customer_type: 'individual', personal_number: PERSONAL_NUMBER, dry_run: true },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { staged: boolean; dry_run?: boolean; preview: Record<string, unknown> }
+
+    expect(result.staged).toBe(false)
+    expect(result.dry_run).toBe(true)
+    expect(result.preview.personal_number_masked).toBe(MASKED)
+    expect(JSON.stringify(result)).not.toContain(PERSONAL_NUMBER)
+    expect(findCall('pending_operations', 'insert')).toBeUndefined()
+  })
+
+  it('replays an identical retry under the same idempotency_key despite the random-IV ciphertext', async () => {
+    const args = {
+      name: 'Anna Andersson',
+      customer_type: 'individual',
+      personal_number: PERSONAL_NUMBER,
+      idempotency_key: '0f2b6f5e-3f2a-4b9e-9c1d-6e9c2a1b7d55',
+    }
+
+    // First call: miss, stage, store.
+    const first = createQueuedMockSupabase()
+    first.enqueue({ data: null }) // company_settings read
+    first.enqueue({ data: null }) // idempotency_keys lookup: miss
+    first.enqueue({ data: { id: 'op-pn-idem' } }) // pending_operations insert
+    first.enqueue({ data: null }) // idempotency_keys store
+    const firstResult = (await tool().execute(args, 'company-1', 'user-1', first.supabase as never)) as {
+      operation_id?: string
+      preview: Record<string, unknown>
+    }
+    expect(firstResult.operation_id).toBe('op-pn-idem')
+    const stored = first.findCall('idempotency_keys', 'insert')?.[0] as {
+      request_hash: string
+      response_body: Record<string, unknown>
+    }
+    // The hash is over the masked preview, which is stable across calls;
+    // hashing params (random-IV ciphertext) would make every retry look like
+    // a different payload and fail with IDEMPOTENCY_KEY_REUSE.
+    expect(stored.request_hash).toBe(
+      hashRequest({ operationType: 'create_customer', params: firstResult.preview, companyId: 'company-1' }),
+    )
+    expect(JSON.stringify(stored)).not.toContain(PERSONAL_NUMBER)
+
+    // Second call: hit with the stored hash; nothing new is staged.
+    const second = createQueuedMockSupabase()
+    second.enqueue({ data: null }) // company_settings read
+    second.enqueue({
+      data: {
+        request_hash: stored.request_hash,
+        response_status: 'success',
+        response_body: stored.response_body,
+        expires_at: '2999-01-01T00:00:00Z',
+      },
+    })
+    const replay = (await tool().execute(args, 'company-1', 'user-1', second.supabase as never)) as {
+      idempotency_replay?: boolean
+      operation_id?: string
+    }
+    expect(replay.idempotency_replay).toBe(true)
+    expect(replay.operation_id).toBe('op-pn-idem')
+    expect(second.findCall('pending_operations', 'insert')).toBeUndefined()
+  })
+})
+
+// ── payment terms ─────────────────────────────────────────────────────
+//
+// #1708: staging hardcoded `|| 30`, so the company's invoice_default_days
+// never reached customers created through MCP even after the web/v1 fix.
+describe('gnubok_create_customer: payment terms', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    eventBus.clear()
+  })
+
+  it('defaults to the company setting when payment_terms is omitted', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: { invoice_default_days: 10 } }) // company_settings read
+    enqueue({ data: { id: 'op-pt-1' } })
+
+    const result = (await tool().execute(
+      { name: 'Kund AB', customer_type: 'swedish_business' },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { preview: Record<string, unknown> }
+
+    expect(result.preview.payment_terms).toBe(10)
+    const inserted = findCall('pending_operations', 'insert')?.[0] as StagedInsert
+    expect(inserted.params.payment_terms).toBe(10)
+  })
+
+  it('falls back to 30 when the company has no default', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: null }) // company_settings read: no row
+    enqueue({ data: { id: 'op-pt-2' } })
+
+    const result = (await tool().execute(
+      { name: 'Kund AB', customer_type: 'swedish_business' },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { preview: Record<string, unknown> }
+
+    expect(result.preview.payment_terms).toBe(30)
+    const inserted = findCall('pending_operations', 'insert')?.[0] as StagedInsert
+    expect(inserted.params.payment_terms).toBe(30)
+  })
+
+  it('keeps an explicit payment_terms without reading the company setting', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: { id: 'op-pt-3' } }) // only the insert: no settings read
+
+    const result = (await tool().execute(
+      { name: 'Kund AB', customer_type: 'swedish_business', payment_terms: 14 },
+      'company-1',
+      'user-1',
+      supabase as never,
+    )) as { staged: boolean; preview: Record<string, unknown> }
+
+    expect(result.staged).toBe(true)
+    expect(result.preview.payment_terms).toBe(14)
+    const inserted = findCall('pending_operations', 'insert')?.[0] as StagedInsert
+    expect(inserted.params.payment_terms).toBe(14)
+  })
+})
diff --git a/extensions/general/mcp-server/__tests__/list-customers.test.ts b/extensions/general/mcp-server/__tests__/list-customers.test.ts
new file mode 100644
index 00000000..0e01ce20
--- /dev/null
+++ b/extensions/general/mcp-server/__tests__/list-customers.test.ts
@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest'
+import { createQueuedMockSupabase } from '@/tests/helpers'
+import { encryptPersonnummer } from '@/lib/salary/personnummer'
+import { tools } from '../server'
+
+const tool = () => tools.find((candidate) => candidate.name === 'gnubok_list_customers')!
+
+// Synthetic personnummer, never a real one.
+const PERSONAL_NUMBER = '19900101-1234'
+const MASKED = '********-1234'
+
+describe('gnubok_list_customers: individual identifiers', () => {
+  it('never lists a personnummer raw: ciphertext is masked, a legacy org_number personnummer is masked and nulled', async () => {
+    const { supabase, enqueue } = createQueuedMockSupabase()
+    enqueue({
+      data: [
+        { id: 'c-1', name: 'Acme AB', customer_type: 'swedish_business', org_number: '556677-8899', personal_number: null },
+        { id: 'c-2', name: 'Anna', customer_type: 'individual', org_number: null, personal_number: encryptPersonnummer(PERSONAL_NUMBER) },
+        // Written before the write paths moved an individual's personnummer
+        // out of org_number (the 2026-08-21 fix); the repair script moves it.
+        { id: 'c-3', name: 'Bertil', customer_type: 'individual', org_number: PERSONAL_NUMBER, personal_number: null },
+        { id: 'c-4', name: 'Cecilia', customer_type: 'individual', org_number: null, personal_number: null },
+      ],
+    })
+
+    const result = (await tool().execute({}, 'company-1', 'user-1', supabase as never)) as {
+      customers: Array<Record<string, unknown>>
+      count: number
+    }
+
+    expect(result.count).toBe(4)
+    const byName = Object.fromEntries(result.customers.map((c) => [c.name as string, c]))
+    expect(byName['Acme AB']).toMatchObject({ org_number: '556677-8899' })
+    expect(byName['Acme AB']).not.toHaveProperty('personal_number')
+    expect(byName['Acme AB']).not.toHaveProperty('personal_number_masked')
+    expect(byName['Anna']).toMatchObject({ org_number: null, personal_number_masked: MASKED })
+    expect(byName['Bertil']).toMatchObject({ org_number: null, personal_number_masked: MASKED })
+    expect(byName['Cecilia']).toMatchObject({ org_number: null, personal_number_masked: null })
+    // Neither the plaintext nor the ciphertext leaves the tool.
+    const serialized = JSON.stringify(result)
+    expect(serialized).not.toContain(PERSONAL_NUMBER)
+    expect(serialized).not.toMatch(/"personal_number"/)
+  })
+})
diff --git a/extensions/general/mcp-server/__tests__/payload-size.bench.test.ts b/extensions/general/mcp-server/__tests__/payload-size.bench.test.ts
index fd9789cc..b7ec9779 100644
--- a/extensions/general/mcp-server/__tests__/payload-size.bench.test.ts
+++ b/extensions/general/mcp-server/__tests__/payload-size.bench.test.ts
@@ -176,9 +176,16 @@ describe('tools/list payload size guard', () => {
     //     longer needs a second staged update after create. The property has
     //     no description (name + maxLength are the whole contract); headroom
     //     before the change was ~11 tokens, so even that minimal form crossed.
+    //   * 59.75K to 59.85K with personal_number on gnubok_create_customer: a
+    //     private person's personnummer had no input at all on the MCP path,
+    //     so agents put it in org_number, where nothing masks it (GDPR art.
+    //     5.1 c; 134 such rows across 10 companies on prod). The property is
+    //     the contract; its description and the org_number/payment_terms
+    //     descriptions were trimmed to one short sentence first; headroom
+    //     before the change was ~11 tokens, so even the trimmed form crossed.
     // Long-term answer to growth is leaning harder on gnubok_search_tools: if this
     // fires again, prefer trimming descriptions or making a tool opt-in via search
     // before bumping further.
-    expect(approxTokens).toBeLessThan(59_750)
+    expect(approxTokens).toBeLessThan(59_850)
   })
 })
diff --git a/extensions/general/mcp-server/__tests__/staging-pii-guard.test.ts b/extensions/general/mcp-server/__tests__/staging-pii-guard.test.ts
index 37b27b90..5e3d2289 100644
--- a/extensions/general/mcp-server/__tests__/staging-pii-guard.test.ts
+++ b/extensions/general/mcp-server/__tests__/staging-pii-guard.test.ts
@@ -29,6 +29,29 @@ describe('assertNoPlaintextPersonnummer', () => {
     ).toThrow(/preview_data contains plaintext PII key "ssn"/)
   })
 
+  it('throws on the customers personal_number key (create_customer must stage the encrypted form)', () => {
+    expect(() =>
+      assertNoPlaintextPersonnummer(
+        { name: 'Anna Andersson', customer_type: 'individual', personal_number: '19900101-1234' },
+        'params',
+      ),
+    ).toThrow(/params contains plaintext PII key "personal_number"/)
+  })
+
+  it('allows the encrypted/masked derivatives that create_customer stages', () => {
+    expect(() =>
+      assertNoPlaintextPersonnummer(
+        {
+          name: 'Anna Andersson',
+          customer_type: 'individual',
+          personal_number_encrypted: 'ab'.repeat(40),
+          personal_number_masked: '********-1234',
+        },
+        'params',
+      ),
+    ).not.toThrow()
+  })
+
   it('allows the encrypted/masked derivatives that create_employee stages', () => {
     expect(() =>
       assertNoPlaintextPersonnummer(
diff --git a/extensions/general/mcp-server/server.ts b/extensions/general/mcp-server/server.ts
index 255edd35..9184669d 100644
--- a/extensions/general/mcp-server/server.ts
+++ b/extensions/general/mcp-server/server.ts
@@ -73,6 +73,21 @@ import {
 } from '@/lib/reports/vat-filing-gate'
 import { findRcBasisGaps } from '@/lib/reports/rc-basis-gaps'
 import { fetchAllRows } from '@/lib/supabase/fetch-all'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+  personalNumberDigits,
+} from '@/lib/customers/personal-number-shape'
+import {
+  PERSONAL_NUMBER_PLAINTEXT_RE,
+  maskCustomerPersonalNumber,
+} from '@/lib/customers/mask-personal-number'
+import {
+  encryptCustomerPersonalNumber,
+  maskStoredCustomerPersonalNumber,
+} from '@/lib/customers/protect-personal-number'
+import { resolveDefaultPaymentTerms } from '@/lib/customers/default-payment-terms'
 import { fetchEntryLines, fetchLinesByEntryIds, type EntryLinesQuery } from '@/lib/bookkeeping/entry-lines'
 import { generateARLedger } from '@/lib/reports/ar-ledger'
 import { generateMonthlyBreakdown } from '@/lib/reports/monthly-breakdown'
@@ -596,6 +611,14 @@ interface StageOptions {
    * Different payload + same key returns IDEMPOTENCY_KEY_REUSE.
    */
   idempotencyKey?: string
+  /**
+   * Payload hashed for the idempotency replay check instead of `params`.
+   * Needed when params carry a non-deterministic derivative of the input
+   * (random-IV ciphertext, see gnubok_create_customer): hashing params would
+   * make an identical retry look like a different payload and fail with
+   * IDEMPOTENCY_KEY_REUSE. Must itself be free of plaintext PII.
+   */
+  idempotencyParams?: Record<string, unknown>
   /**
    * ISO yyyy-MM-dd date used to look up period_status before staging. When
    * provided, the response includes a `period_status` envelope so agents and
@@ -699,7 +722,7 @@ async function stagePendingOperation(
   //    same key UUID submitted under a different company is treated as a
   //    fresh request, not a replay.
   const requestHash = options.idempotencyKey
-    ? hashRequest({ operationType, params, companyId })
+    ? hashRequest({ operationType, params: options.idempotencyParams ?? params, companyId })
     : null
   if (options.idempotencyKey && requestHash) {
     const cached = await checkIdempotencyKey(supabase, userId, companyId, options.idempotencyKey, requestHash)
@@ -4593,12 +4616,19 @@ export const tools: McpTool[] = [
     async execute(_args, companyId, userId, supabase) {
       // Paginated (fetchAllRows): PostgREST silently caps un-ranged selects at
       // 1000 rows. Page on the unique id, then re-sort by name for display.
-      let customers: { id: string; name: string }[]
+      type ListedCustomer = {
+        id: string
+        name: string
+        customer_type: string
+        org_number: string | null
+        personal_number: string | null
+      }
+      let rows: ListedCustomer[]
       try {
-        customers = await fetchAllRows<{ id: string; name: string }>(({ from, to }) =>
+        rows = await fetchAllRows<ListedCustomer>(({ from, to }) =>
           supabase
             .from('customers')
-            .select('id, name, customer_type, email, org_number, vat_number, default_payment_terms, city, country')
+            .select('id, name, customer_type, email, org_number, vat_number, personal_number, default_payment_terms, city, country')
             .eq('company_id', companyId)
             .order('id', { ascending: true })
             .range(from, to)
@@ -4606,7 +4636,26 @@ export const tools: McpTool[] = [
       } catch (error) {
         throw new Error(`Database error: ${error instanceof Error ? error.message : 'unknown error'}`)
       }
-      customers.sort((a, b) => a.name.localeCompare(b.name, 'sv') || a.id.localeCompare(b.id))
+      rows.sort((a, b) => a.name.localeCompare(b.name, 'sv') || a.id.localeCompare(b.id))
+
+      // GDPR art. 5.1 c, same rule as the v1 list: an individual's
+      // personnummer never leaves this tool raw. personal_number is stored as
+      // ciphertext and is exposed only as personal_number_masked
+      // (********-1234); a legacy individual row that still carries the
+      // personnummer in org_number (written before the write paths started
+      // moving it into personal_number) shows it masked the same way, and its
+      // org_number is nulled rather than listed.
+      const customers = rows.map(({ personal_number, ...customer }) => {
+        if (customer.customer_type !== 'individual') return customer
+        const legacyInOrgNumber = orgNumberHoldsPersonalNumber(customer.customer_type, customer.org_number)
+        return {
+          ...customer,
+          org_number: legacyInOrgNumber ? null : customer.org_number,
+          personal_number_masked:
+            maskStoredCustomerPersonalNumber(personal_number)
+            ?? (legacyInOrgNumber ? maskCustomerPersonalNumber(customer.org_number) : null),
+        }
+      })
 
       return { customers, count: customers.length }
     },
@@ -4629,9 +4678,10 @@ export const tools: McpTool[] = [
         },
         customer_number: { type: 'string', maxLength: 32 },
         email: { type: 'string', description: 'Email address' },
-        org_number: { type: 'string', description: 'Swedish org number' },
+        org_number: { type: 'string', description: 'Swedish org number (business types). A personnummer belongs in personal_number.' },
+        personal_number: { type: 'string', description: 'Personnummer for customer_type=individual. Encrypted at staging, masked on read.' },
         vat_number: { type: 'string', description: 'EU VAT number' },
-        payment_terms: { type: 'number', description: 'Payment terms in days (default 30)' },
+        payment_terms: { type: 'number', description: 'Days. Default: the company setting, else 30.' },
         address: { type: 'string', description: 'Street address' },
         postal_code: { type: 'string' },
         city: { type: 'string' },
@@ -4672,24 +4722,83 @@ export const tools: McpTool[] = [
         throw new Error('customer_number must be at most 32 characters.')
       }
 
-      const params = {
+      // Identifiers. A personnummer belongs in personal_number on an
+      // individual and nowhere else. The business-type guard mirrors
+      // CreateCustomerSchema (nothing masks org_number, GDPR art. 5.1 c); a
+      // personnummer-shaped org_number on an individual is the personnummer
+      // submitted in the wrong field, which is all an agent COULD do before
+      // this tool had a personal_number input, so it is moved rather than
+      // refused. Everything is checked here, at staging, so the user never
+      // approves an operation that then fails at commit.
+      const orgNumberArg = typeof args.org_number === 'string' ? args.org_number.trim() : ''
+      const personalNumberArg = typeof args.personal_number === 'string' ? args.personal_number.trim() : ''
+      if (orgNumberArg && customerType !== 'individual' && looksLikeSwedishPersonalNumber(orgNumberArg)) {
+        throw new Error(
+          'org_number looks like a Swedish personal identity number (personnummer). Create the customer with '
+          + 'customer_type "individual" and pass the number as personal_number instead, so it is stored encrypted '
+          + 'and masked in lists.',
+        )
+      }
+      if (personalNumberArg && customerType !== 'individual') {
+        throw new Error('personal_number is only allowed for customer_type "individual".')
+      }
+      let orgNumber: string | null = orgNumberArg || null
+      let personalNumber: string | null = personalNumberArg || null
+      if (orgNumberHoldsPersonalNumber(customerType, orgNumber)) {
+        const rerouted = normalizeReroutedPersonalNumber(orgNumber!)
+        if (personalNumber && personalNumberDigits(personalNumber) !== personalNumberDigits(rerouted)) {
+          throw new Error(
+            'org_number looks like a personnummer and differs from personal_number. An individual customer keeps '
+            + 'its personnummer in personal_number; leave org_number empty.',
+          )
+        }
+        personalNumber = personalNumber ?? rerouted
+        orgNumber = null
+      }
+      if (personalNumber && !PERSONAL_NUMBER_PLAINTEXT_RE.test(personalNumber)) {
+        throw new Error('personal_number must be a Swedish personnummer: YYYYMMDD-XXXX, YYMMDD-XXXX or the digits alone.')
+      }
+
+      // Resolved at staging, not at commit, so the approval preview shows the
+      // terms the row will actually get: the caller's value, else the
+      // company's invoice_default_days, else 30. (Staging `|| 30` here is why
+      // #1708's fix never reached the MCP path.)
+      const paymentTermsArg = Number(args.payment_terms)
+      const paymentTerms = await resolveDefaultPaymentTerms(
+        supabase,
+        companyId,
+        Number.isFinite(paymentTermsArg) && paymentTermsArg > 0 ? paymentTermsArg : undefined,
+      )
+
+      const preview: Record<string, unknown> = {
         name: name.trim(),
         customer_type: customerType,
         customer_number: customerNumber || null,
         email: (args.email as string) || null,
-        org_number: (args.org_number as string) || null,
+        org_number: orgNumber,
         vat_number: (args.vat_number as string) || null,
-        payment_terms: Number(args.payment_terms) || 30,
+        payment_terms: paymentTerms,
         address: (args.address as string) || null,
         postal_code: (args.postal_code as string) || null,
         city: (args.city as string) || null,
         country: (args.country as string) || 'Sweden',
+        // The preview (and the approval UI that renders it) only ever sees
+        // the masked form.
+        personal_number_masked: personalNumber ? maskCustomerPersonalNumber(personalNumber) : null,
+      }
+      // PII rule (staging-pii-guard): pending_operations.params never holds
+      // a plaintext personnummer. Encrypted here, same as create_employee;
+      // the executor stores the ciphertext as-is.
+      const { personal_number_masked: _masked, ...paramsBase } = preview
+      const params: Record<string, unknown> = {
+        ...paramsBase,
+        personal_number_encrypted: personalNumber ? encryptCustomerPersonalNumber(personalNumber) : null,
       }
 
       return stagePendingOperation(supabase, companyId, userId, 'create_customer',
-        `Ny kund: ${params.name}`,
+        `Ny kund: ${preview.name as string}`,
         params,
-        params, // params ARE the preview for customers
+        preview,
         actor,
         {
           description: 'Once approved, you can invoice this customer with gnubok_create_invoice using the returned customer_id.',
@@ -4698,6 +4807,9 @@ export const tools: McpTool[] = [
         {
           dryRun: Boolean(args.dry_run),
           idempotencyKey: typeof args.idempotency_key === 'string' ? args.idempotency_key : undefined,
+          // The ciphertext has a random IV, so params differ on every call;
+          // the masked preview is the stable identity of the request.
+          idempotencyParams: preview,
         }
       )
     },
diff --git a/extensions/general/mcp-server/skills/customer-onboarding.ts b/extensions/general/mcp-server/skills/customer-onboarding.ts
index b857b339..85e1c06d 100644
--- a/extensions/general/mcp-server/skills/customer-onboarding.ts
+++ b/extensions/general/mcp-server/skills/customer-onboarding.ts
@@ -21,8 +21,9 @@ later: much cheaper to ask the customer once at onboarding.
 
 | Customer | customer_type | Required fields | VAT treatment |
 |---|---|---|---|
-| Swedish private person | \`individual\` | name | 25/12/6 % standard, no reverse charge |
-| Swedish AB / HB / KB / EF | \`swedish_business\` | name, org_number | 25/12/6 % standard |
+| Swedish private person | \`individual\` | name, personal_number (optional; encrypted, masked on read) | 25/12/6 % standard, no reverse charge |
+| Swedish AB / HB / KB | \`swedish_business\` | name, org_number | 25/12/6 % standard |
+| Swedish enskild firma (EF) | \`individual\` | name, personal_number (an EF's org number IS the owner's personnummer; a business type refuses it) | 25/12/6 % standard |
 | EU company (VAT-registered) | \`eu_business\` | name, vat_number (validated) | Reverse charge (varor + tjänster): invoice has 0 % VAT, customer pays VAT in their country |
 | EU company (no VAT number) | \`eu_business\` | name, country | Treated as individual: 25 % charged, no reverse charge |
 | Non-EU company | \`non_eu_business\` | name, country | Export 0 % (varor) or reverse charge per service rules |
@@ -102,7 +103,7 @@ ROT/RUT-avdrag applies to physical persons receiving home-services
 required on the invoice. Update the customer record with:
 
 - \`fastighetsbeteckning\` (property identifier, for ROT)
-- \`personnummer\` (encrypted at rest)
+- \`personal_number\` (set at creation via \`gnubok_create_customer\` or in the web form; encrypted at rest, masked on read)
 
 Then create the invoice with ROT/RUT flag set. See the \`invoicing-rules\` skill
 for the booking details (BAS accounts 1513 + 3740).
diff --git a/extensions/general/mcp-server/staging-pii-guard.ts b/extensions/general/mcp-server/staging-pii-guard.ts
index 79cf605e..1069afbf 100644
--- a/extensions/general/mcp-server/staging-pii-guard.ts
+++ b/extensions/general/mcp-server/staging-pii-guard.ts
@@ -3,9 +3,11 @@
  *
  * pending_operations.params and .preview_data are persisted verbatim and
  * rendered in approval UIs, so no staging payload may carry a plaintext
- * personnummer. The one tool that legitimately receives one
- * (gnubok_create_employee) encrypts at staging time and stores only
- * `personnummer_encrypted` / `personnummer_last4` / `personnummer_masked`.
+ * personnummer. The tools that legitimately receive one
+ * (gnubok_create_employee, gnubok_create_customer) encrypt at staging time and
+ * store only `personnummer_encrypted` / `personnummer_last4` /
+ * `personnummer_masked` (employees) or `personal_number_encrypted` /
+ * `personal_number_masked` (customers).
  * This guard runs inside stagePendingOperation, so every current and FUTURE
  * staging tool inherits the rule: a tool that forgets to encrypt fails loudly
  * at staging instead of silently persisting PII.
@@ -16,7 +18,15 @@
  * forms above are therefore allowed by construction.
  */
 
-const FORBIDDEN_KEYS = new Set(['personnummer', 'pnr', 'social_security_number', 'ssn'])
+const FORBIDDEN_KEYS = new Set([
+  'personnummer',
+  'pnr',
+  'social_security_number',
+  'ssn',
+  // customers.personal_number: gnubok_create_customer stages it as
+  // personal_number_encrypted + personal_number_masked, never under this key.
+  'personal_number',
+])
 
 /**
  * Cycle/degenerate-payload stop: staged payloads are shallow JSON. Anything
diff --git a/lib/api/__tests__/schemas.test.ts b/lib/api/__tests__/schemas.test.ts
index 8dacc002..c1dfe519 100644
--- a/lib/api/__tests__/schemas.test.ts
+++ b/lib/api/__tests__/schemas.test.ts
@@ -729,6 +729,79 @@ describe('CreateCustomerSchema', () => {
   })
 })
 
+// Where an individual's personnummer lands (#1707 follow-up). Synthetic
+// personnummer throughout, never a real one.
+describe('CreateCustomerSchema: personnummer placement', () => {
+  it('moves a personnummer-shaped org_number on an individual into personal_number', () => {
+    const result = CreateCustomerSchema.safeParse({
+      name: 'Anna Andersson',
+      customer_type: 'individual',
+      org_number: '19900101-1234',
+    })
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.personal_number).toBe('19900101-1234')
+      expect(result.data.org_number).toBeUndefined()
+    }
+  })
+
+  it('strips whitespace from the moved value so it matches the personnummer input forms', () => {
+    const result = CreateCustomerSchema.safeParse({
+      name: 'Anna Andersson',
+      customer_type: 'individual',
+      org_number: '19900101 1234',
+    })
+    expect(result.success).toBe(true)
+    if (result.success) expect(result.data.personal_number).toBe('199001011234')
+  })
+
+  it('drops org_number when it duplicates personal_number', () => {
+    const result = CreateCustomerSchema.safeParse({
+      name: 'Anna Andersson',
+      customer_type: 'individual',
+      org_number: '199001011234',
+      personal_number: '19900101-1234',
+    })
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.personal_number).toBe('19900101-1234')
+      expect(result.data.org_number).toBeUndefined()
+    }
+  })
+
+  it('rejects an org_number that is a different personnummer than personal_number', () => {
+    const result = CreateCustomerSchema.safeParse({
+      name: 'Anna Andersson',
+      customer_type: 'individual',
+      org_number: '19850505-5555',
+      personal_number: '19900101-1234',
+    })
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(result.error.issues.some((issue) => issue.path.join('.') === 'org_number')).toBe(true)
+    }
+  })
+
+  it('still rejects a personnummer-shaped org_number on a business customer', () => {
+    const result = CreateCustomerSchema.safeParse(validCustomer({ org_number: '19900101-1234' }))
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(result.error.issues.some((issue) => issue.path.join('.') === 'org_number')).toBe(true)
+    }
+  })
+
+  it('leaves a legal-entity organisationsnummer alone on every customer_type', () => {
+    for (const customer_type of ['individual', 'swedish_business'] as const) {
+      const result = CreateCustomerSchema.safeParse({ name: 'X', customer_type, org_number: '556677-8899' })
+      expect(result.success).toBe(true)
+      if (result.success) {
+        expect(result.data.org_number).toBe('556677-8899')
+        expect(result.data.personal_number).toBeUndefined()
+      }
+    }
+  })
+})
+
 // ============================================================
 // Supplier schemas
 // ============================================================
diff --git a/lib/api/schemas.ts b/lib/api/schemas.ts
index d9333351..625f230b 100644
--- a/lib/api/schemas.ts
+++ b/lib/api/schemas.ts
@@ -22,7 +22,12 @@ import {
 } from '@/lib/invoices/rot-rut-rules'
 import { NON_IBAN_CURRENCIES } from '@/lib/invoices/payment-accounts'
 import { PERSONAL_NUMBER_INPUT_RE } from '@/lib/customers/mask-personal-number'
-import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+  personalNumberDigits,
+} from '@/lib/customers/personal-number-shape'
 import type { AuditAction, Currency } from '@/types'
 import type { BankFileFormatId } from '@/lib/import/bank-file/types'
 
@@ -951,6 +956,23 @@ export const CreateCustomerSchema = z.object({
         + 'instead, so it is stored encrypted and masked in list responses.',
     })
   }
+  // An individual's personnummer submitted as org_number is moved into
+  // personal_number by the transform below. Next to a DIFFERENT
+  // personal_number in the same body the two conflict, and guessing which
+  // one the caller meant is worse than a 400.
+  if (
+    customer.personal_number
+    && orgNumberHoldsPersonalNumber(customer.customer_type, customer.org_number)
+    && personalNumberDigits(customer.org_number!) !== personalNumberDigits(customer.personal_number)
+  ) {
+    ctx.addIssue({
+      code: 'custom',
+      path: ['org_number'],
+      message:
+        'org_number looks like a Swedish personal identity number (personnummer) and differs from '
+        + 'personal_number. An individual customer keeps its personnummer in personal_number; leave org_number empty.',
+    })
+  }
   if (
     (customer.invoice_email_cc_addresses?.length ?? 0)
     + (customer.invoice_email_bcc_addresses?.length ?? 0)
@@ -962,6 +984,21 @@ export const CreateCustomerSchema = z.object({
       message: `At most ${MAX_INVOICE_EMAIL_COPY_RECIPIENTS} customer invoice copy recipients are allowed in total`,
     })
   }
+}).transform((customer) => {
+  // A personnummer-shaped org_number on customer_type='individual' IS the
+  // personnummer, submitted in the wrong field (the MCP create tool had no
+  // personal_number input until 2026-08-21, and the v1 docs long said
+  // "org_number accepted as input" for individuals). Nothing masks
+  // org_number, so it is moved into personal_number, where the routes
+  // encrypt it and every read returns ********-1234, and org_number is left
+  // empty. With an equal personal_number already present only the duplicate
+  // is dropped; an unequal one was refused above.
+  if (!orgNumberHoldsPersonalNumber(customer.customer_type, customer.org_number)) return customer
+  return {
+    ...customer,
+    org_number: undefined,
+    personal_number: customer.personal_number || normalizeReroutedPersonalNumber(customer.org_number!),
+  }
 })
 
 export const UpdateCustomerSchema = z.object({
diff --git a/lib/customers/__tests__/mask-personal-number.test.ts b/lib/customers/__tests__/mask-personal-number.test.ts
new file mode 100644
index 00000000..d12496fb
--- /dev/null
+++ b/lib/customers/__tests__/mask-personal-number.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from 'vitest'
+import {
+  PERSONAL_NUMBER_PLAINTEXT_RE,
+  UNDECRYPTABLE_PERSONAL_NUMBER_MASK,
+  customerListIdentifier,
+} from '@/lib/customers/mask-personal-number'
+
+// Synthetic personnummer throughout, never a real one.
+describe('customerListIdentifier', () => {
+  it('shows org_number for business rows', () => {
+    expect(customerListIdentifier({ customer_type: 'swedish_business', org_number: '556677-8899' })).toBe('556677-8899')
+    expect(customerListIdentifier({ customer_type: 'swedish_business', org_number: null })).toBe('')
+  })
+
+  it('shows the masked personal_number for individual rows, passing an API mask through', () => {
+    expect(customerListIdentifier({ customer_type: 'individual', personal_number: '********-1234' })).toBe('********-1234')
+    expect(customerListIdentifier({ customer_type: 'individual', personal_number: '19900101-1234' })).toBe('********-1234')
+    expect(
+      customerListIdentifier({ customer_type: 'individual', personal_number: UNDECRYPTABLE_PERSONAL_NUMBER_MASK }),
+    ).toBe(UNDECRYPTABLE_PERSONAL_NUMBER_MASK)
+  })
+
+  it('masks a legacy individual row that still carries its personnummer in org_number', () => {
+    expect(customerListIdentifier({ customer_type: 'individual', org_number: '19900101-1234', personal_number: null })).toBe(
+      '********-1234',
+    )
+  })
+
+  it('leaves a non-personnummer org_number on an individual visible', () => {
+    expect(customerListIdentifier({ customer_type: 'individual', org_number: 'CHE-123.456.789' })).toBe('CHE-123.456.789')
+    expect(customerListIdentifier({ customer_type: 'individual' })).toBe('')
+  })
+})
+
+describe('PERSONAL_NUMBER_PLAINTEXT_RE', () => {
+  it('accepts the four written forms and nothing else', () => {
+    for (const value of ['900101-1234', '900101+1234', '19900101-1234', '9001011234', '199001011234']) {
+      expect(PERSONAL_NUMBER_PLAINTEXT_RE.test(value)).toBe(true)
+    }
+    // Shape only: a legal-entity orgnr with a dash has the same digit shape
+    // and is kept out by looksLikeSwedishPersonalNumber at the call sites,
+    // not by this regex.
+    for (const value of ['********-1234', '********-????', '19900101 1234', 'abc', '1234']) {
+      expect(PERSONAL_NUMBER_PLAINTEXT_RE.test(value)).toBe(false)
+    }
+  })
+})
diff --git a/lib/customers/__tests__/personal-number-shape.test.ts b/lib/customers/__tests__/personal-number-shape.test.ts
index 535dd410..354acc67 100644
--- a/lib/customers/__tests__/personal-number-shape.test.ts
+++ b/lib/customers/__tests__/personal-number-shape.test.ts
@@ -1,5 +1,10 @@
 import { describe, expect, it } from 'vitest'
-import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+  personalNumberDigits,
+} from '@/lib/customers/personal-number-shape'
 
 // Every personal-shaped fixture is synthetic, never a real person's number.
 describe('looksLikeSwedishPersonalNumber', () => {
@@ -40,3 +45,37 @@ describe('looksLikeSwedishPersonalNumber', () => {
     expect(looksLikeSwedishPersonalNumber('************')).toBe(false)
   })
 })
+
+describe('orgNumberHoldsPersonalNumber', () => {
+  it('is true only for an individual whose org_number has personnummer shape', () => {
+    expect(orgNumberHoldsPersonalNumber('individual', '19900101-1234')).toBe(true)
+    expect(orgNumberHoldsPersonalNumber('individual', '9001011234')).toBe(true)
+    expect(orgNumberHoldsPersonalNumber('individual', '19900101 1234')).toBe(true)
+  })
+
+  it('is false for business types, legal-entity org numbers, and empty values', () => {
+    // A business carrying a personnummer is the other guard's job (reject),
+    // not a reroute.
+    expect(orgNumberHoldsPersonalNumber('swedish_business', '19900101-1234')).toBe(false)
+    expect(orgNumberHoldsPersonalNumber('individual', '556677-8899')).toBe(false)
+    expect(orgNumberHoldsPersonalNumber('individual', '')).toBe(false)
+    expect(orgNumberHoldsPersonalNumber('individual', '   ')).toBe(false)
+    expect(orgNumberHoldsPersonalNumber('individual', null)).toBe(false)
+    expect(orgNumberHoldsPersonalNumber('individual', undefined)).toBe(false)
+    expect(orgNumberHoldsPersonalNumber(undefined, '19900101-1234')).toBe(false)
+  })
+})
+
+describe('normalizeReroutedPersonalNumber / personalNumberDigits', () => {
+  it('drops whitespace but keeps the separator', () => {
+    expect(normalizeReroutedPersonalNumber('19900101 1234')).toBe('199001011234')
+    expect(normalizeReroutedPersonalNumber(' 19900101-1234 ')).toBe('19900101-1234')
+    expect(normalizeReroutedPersonalNumber('900101+1234')).toBe('900101+1234')
+  })
+
+  it('compares across written forms by digits only', () => {
+    expect(personalNumberDigits('19900101-1234')).toBe('199001011234')
+    expect(personalNumberDigits('19900101-1234')).toBe(personalNumberDigits('199001011234'))
+    expect(personalNumberDigits('900101-1234')).not.toBe(personalNumberDigits('19900101-1234'))
+  })
+})
diff --git a/lib/customers/mask-personal-number.ts b/lib/customers/mask-personal-number.ts
index f57152a5..72be423a 100644
--- a/lib/customers/mask-personal-number.ts
+++ b/lib/customers/mask-personal-number.ts
@@ -7,6 +7,8 @@
  * half lives in lib/customers/protect-personal-number.ts, which is server-only.
  */
 
+import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+
 /**
  * Placeholder used when a stored personal_number cannot be decrypted
  * (corrupted ciphertext, a value written under a different
@@ -53,6 +55,13 @@ export function isMaskedPersonalNumber(value: unknown): boolean {
  */
 export const PERSONAL_NUMBER_INPUT_RE = /^(?:(?:\d{6}|\d{8})[-+]?\d{4}|\*{8}-(?:\d{4}|\?{4}))$/
 
+/**
+ * The plaintext half alone: the four accepted written forms of a personnummer
+ * (YYMMDD-XXXX, YYMMDD+XXXX, YYYYMMDD-XXXX, or the 10/12 digits). What a create
+ * path accepts.
+ */
+export const PERSONAL_NUMBER_PLAINTEXT_RE = /^(?:\d{6}|\d{8})[-+]?\d{4}$/
+
 /**
  * Display a personal identity number without exposing birth date or full ID.
  *
@@ -67,3 +76,30 @@ export function maskCustomerPersonalNumber(value: string | null | undefined): st
   const last4 = value.replace(/\D/g, '').slice(-4)
   return last4.length === 4 ? `********-${last4}` : null
 }
+
+/**
+ * The identifier a customer LIST may show for a row, never a raw personnummer.
+ *
+ * Business rows show org_number (Bolagsverket-public). Individual rows show
+ * the masked personal_number; a legacy individual row that still carries its
+ * personnummer in org_number (written before the write paths started moving
+ * it, see lib/customers/personal-number-shape.ts) shows that value masked the
+ * same way instead of raw. Callers pass rows whose personal_number is already
+ * the API's masked form or a plaintext value; ciphertext must be masked
+ * server-side first (maskStoredCustomerPersonalNumber).
+ */
+export function customerListIdentifier(row: {
+  customer_type?: string | null
+  org_number?: string | null
+  personal_number?: string | null
+}): string {
+  if (row.customer_type !== 'individual') {
+    return row.org_number || row.personal_number || ''
+  }
+  if (row.personal_number) return maskCustomerPersonalNumber(row.personal_number) ?? ''
+  const orgNumber = row.org_number || ''
+  if (orgNumber && looksLikeSwedishPersonalNumber(orgNumber)) {
+    return maskCustomerPersonalNumber(orgNumber) ?? ''
+  }
+  return orgNumber
+}
diff --git a/lib/customers/personal-number-shape.ts b/lib/customers/personal-number-shape.ts
index aca33b75..23b355f8 100644
--- a/lib/customers/personal-number-shape.ts
+++ b/lib/customers/personal-number-shape.ts
@@ -37,3 +37,42 @@ export function looksLikeSwedishPersonalNumber(value: string): boolean {
   const birthDay = day > 60 ? day - 60 : day
   return birthDay >= 1 && birthDay <= 31
 }
+
+/**
+ * True when a customer row's org_number is really its personnummer: the row
+ * is an individual (privatperson) and the value has personnummer shape.
+ *
+ * Every write path treats that combination as "personnummer submitted in the
+ * wrong field": the value is moved into personal_number (encrypted, masked on
+ * read) and org_number is left empty. Nothing masks org_number, so leaving it
+ * there is exactly the unmasked-identifier leak the business-type guard above
+ * exists to prevent; and the MCP create tool had no personal_number input at
+ * all until 2026-08-21, so agents had nowhere else to put it.
+ */
+export function orgNumberHoldsPersonalNumber(
+  customerType: string | null | undefined,
+  orgNumber: string | null | undefined,
+): boolean {
+  return (
+    customerType === 'individual'
+    && typeof orgNumber === 'string'
+    && orgNumber.trim() !== ''
+    && looksLikeSwedishPersonalNumber(orgNumber)
+  )
+}
+
+/**
+ * The personnummer as it should be stored once it has been lifted out of
+ * org_number: separators are kept (the encrypt path accepts any of the four
+ * input forms) but whitespace is dropped, because "19900101 1234" passes the
+ * shape check yet fails PERSONAL_NUMBER_INPUT_RE and the legacy-plaintext
+ * reveal regex.
+ */
+export function normalizeReroutedPersonalNumber(orgNumber: string): string {
+  return orgNumber.replace(/\s+/g, '')
+}
+
+/** Digits only, for comparing a personnummer across its written forms. */
+export function personalNumberDigits(value: string): string {
+  return value.replace(/\D/g, '')
+}
diff --git a/lib/errors/structured-errors.ts b/lib/errors/structured-errors.ts
index ba619411..6c33328c 100644
--- a/lib/errors/structured-errors.ts
+++ b/lib/errors/structured-errors.ts
@@ -2409,6 +2409,13 @@ const ARTICLE: Record<string, StructuredErrorEntry> = {
     message_en:
       'The org number looks like a Swedish personal identity number. Save the customer as an individual instead, so the number is stored protected and masked in lists.',
   },
+  CUSTOMER_PERSONAL_NUMBER_CONFLICT: {
+    httpStatus: 400,
+    message_sv:
+      'Kunden fick två olika personnummer: ett i fältet personnummer och ett i fältet organisationsnummer. En privatperson har sitt personnummer i fältet personnummer; lämna organisationsnumret tomt.',
+    message_en:
+      'The customer was given two different personal identity numbers: one in personal_number and one in org_number. An individual customer keeps its personnummer in personal_number; leave org_number empty.',
+  },
   ARTICLE_DELETE_FAILED: {
     httpStatus: 500,
     message_sv: 'Artikeln kunde inte tas bort.',
diff --git a/lib/pending-operations/__tests__/executors.test.ts b/lib/pending-operations/__tests__/executors.test.ts
index fc22a23c..154584e0 100644
--- a/lib/pending-operations/__tests__/executors.test.ts
+++ b/lib/pending-operations/__tests__/executors.test.ts
@@ -14,6 +14,7 @@ import {
   makeSupplierInvoice,
 } from '@/tests/helpers'
 import type { PendingOperation } from '@/types'
+import { decryptPersonnummer, encryptPersonnummer } from '@/lib/salary/personnummer'
 
 vi.mock('@/lib/core/bookkeeping/period-service', async () => {
   const actual = await vi.importActual<typeof import('@/lib/core/bookkeeping/period-service')>(
@@ -277,6 +278,80 @@ describe('commitPendingOperation: create_customer', () => {
     expect(result.status).toBe('committed')
     expect(findCall('customers', 'insert')?.[0]).toMatchObject({ customer_number: null })
   })
+
+  // Synthetic personnummer, never a real one. Ciphertext shape enforced by
+  // customers_personal_number_check (20260726110000).
+  const PERSONAL_NUMBER = '19900101-1234'
+  const CIPHERTEXT_SHAPE = /^[0-9a-f]{76,255}$/
+
+  it('stores the staged personal_number_encrypted as the customer personal_number, with the staged payment terms', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: { id: 'op-1' }, error: null }) // CAS claim
+    // payment_terms were resolved at staging, so no company_settings read here
+    enqueue({ data: makeCustomer({ id: 'cust-1', customer_type: 'individual' }), error: null }) // customers insert
+    enqueue({ data: null, error: null }) // dispatcher's pending_operations update
+
+    const encrypted = encryptPersonnummer(PERSONAL_NUMBER)
+    const op = makePendingOp({
+      operation_type: 'create_customer',
+      params: {
+        name: 'Anna Andersson',
+        customer_type: 'individual',
+        payment_terms: 10,
+        personal_number_encrypted: encrypted,
+      },
+    })
+
+    const result = await commitPendingOperation(supabase as never, 'user-1', 'company-1', op)
+
+    expect(result.status).toBe('committed')
+    expect(findCall('customers', 'insert')?.[0]).toMatchObject({
+      personal_number: encrypted,
+      org_number: null,
+      default_payment_terms: 10,
+    })
+  })
+
+  it('moves a personnummer staged as org_number on an individual into personal_number, encrypted', async () => {
+    // An operation staged before gnubok_create_customer had a personal_number
+    // input, committed after this deploy.
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: { id: 'op-1' }, error: null }) // CAS claim
+    enqueue({ data: null, error: null }) // company_settings read (payment-terms default)
+    enqueue({ data: makeCustomer({ id: 'cust-1', customer_type: 'individual' }), error: null }) // customers insert
+    enqueue({ data: null, error: null }) // dispatcher's pending_operations update
+
+    const op = makePendingOp({
+      operation_type: 'create_customer',
+      params: { name: 'Bertil Bengtsson', customer_type: 'individual', org_number: PERSONAL_NUMBER },
+    })
+
+    const result = await commitPendingOperation(supabase as never, 'user-1', 'company-1', op)
+
+    expect(result.status).toBe('committed')
+    const inserted = findCall('customers', 'insert')?.[0] as { org_number: string | null; personal_number: string | null }
+    expect(inserted.org_number).toBeNull()
+    expect(inserted.personal_number).toMatch(CIPHERTEXT_SHAPE)
+    expect(decryptPersonnummer(inserted.personal_number!)).toBe(PERSONAL_NUMBER)
+    expect(JSON.stringify(inserted)).not.toContain(PERSONAL_NUMBER)
+  })
+
+  it('still refuses a personnummer-shaped org_number on a business customer', async () => {
+    const { supabase, enqueue, findCall } = createQueuedMockSupabase()
+    enqueue({ data: { id: 'op-1' }, error: null }) // CAS claim
+    enqueue({ data: null, error: null }) // dispatcher's reject update
+
+    const op = makePendingOp({
+      operation_type: 'create_customer',
+      params: { name: 'Enskild Firma X', customer_type: 'swedish_business', org_number: PERSONAL_NUMBER },
+    })
+
+    const result = await commitPendingOperation(supabase as never, 'user-1', 'company-1', op)
+
+    expect(result.status).toBe('failed')
+    expect(result.http_status).toBe(400)
+    expect(findCall('customers', 'insert')).toBeUndefined()
+  })
 })
 
 describe('commitPendingOperation: credit-note issuance guard', () => {
diff --git a/lib/pending-operations/commit.ts b/lib/pending-operations/commit.ts
index 25ce8b8b..b02833b4 100644
--- a/lib/pending-operations/commit.ts
+++ b/lib/pending-operations/commit.ts
@@ -25,7 +25,12 @@ import {
 import { roundOre } from '@/lib/money'
 import { getErrorMessage } from '@/lib/errors/get-error-message'
 import { validateVatNumber } from '@/lib/vat/vies-client'
-import { looksLikeSwedishPersonalNumber } from '@/lib/customers/personal-number-shape'
+import {
+  looksLikeSwedishPersonalNumber,
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+} from '@/lib/customers/personal-number-shape'
+import { encryptCustomerPersonalNumber } from '@/lib/customers/protect-personal-number'
 import { resolveDefaultPaymentTerms } from '@/lib/customers/default-payment-terms'
 import {
   normalizeVatRateToDecimal,
@@ -359,7 +364,7 @@ async function commitCreateCustomer(
   // Same GDPR guard as CreateCustomerSchema: identifiers are only masked on
   // customer_type='individual' rows, so a personnummer stored as a business
   // org_number would be shown unmasked everywhere.
-  const orgNumber = (params.org_number as string) || null
+  let orgNumber = (params.org_number as string) || null
   if (
     orgNumber &&
     params.customer_type !== 'individual' &&
@@ -373,6 +378,21 @@ async function commitCreateCustomer(
     }
   }
 
+  // The personnummer arrives from staging already encrypted
+  // (personal_number_encrypted; params never hold the plaintext). An
+  // operation staged before gnubok_create_customer had a personal_number
+  // input may still carry the personnummer in org_number on an individual:
+  // it is stored encrypted in personal_number and org_number is cleared,
+  // same as every other write path.
+  let personalNumberEncrypted =
+    typeof params.personal_number_encrypted === 'string' && params.personal_number_encrypted
+      ? params.personal_number_encrypted
+      : null
+  if (orgNumberHoldsPersonalNumber(params.customer_type as string, orgNumber)) {
+    personalNumberEncrypted ??= encryptCustomerPersonalNumber(normalizeReroutedPersonalNumber(orgNumber!))
+    orgNumber = null
+  }
+
   // Unset payment terms follow the company's own default, not a hardcoded 30.
   const defaultPaymentTerms = await resolveDefaultPaymentTerms(
     supabase,
@@ -391,6 +411,7 @@ async function commitCreateCustomer(
       email: (params.email as string) || null,
       org_number: orgNumber,
       vat_number: (params.vat_number as string) || null,
+      personal_number: personalNumberEncrypted,
       default_payment_terms: defaultPaymentTerms,
       address_line1: (params.address as string) || null,
       postal_code: (params.postal_code as string) || null,
diff --git a/scripts/repair-customer-personal-number-in-org-number.ts b/scripts/repair-customer-personal-number-in-org-number.ts
new file mode 100644
index 00000000..4c8e97bb
--- /dev/null
+++ b/scripts/repair-customer-personal-number-in-org-number.ts
@@ -0,0 +1,169 @@
+/**
+ * One-off repair: move an individual customer's personnummer out of
+ * customers.org_number into customers.personal_number (encrypted).
+ *
+ * WHY: until 2026-08-21 the MCP gnubok_create_customer tool had no
+ * personal_number input, the v1 REST docs said org_number was "accepted as
+ * input" for individuals, and nothing masks org_number. So a customer_type=
+ * 'individual' row could carry its personnummer in org_number, where the
+ * web customer list, the v1 detail endpoint and the MCP customer list showed
+ * it raw (GDPR art. 5.1 c). The code fix moves such a value into
+ * personal_number on every write path; this repairs the rows already in the
+ * DB. Run AFTER the code fix is deployed (the read paths mask these rows in
+ * the meantime, but the data should not stay there).
+ *
+ * Selection: customer_type='individual' AND org_number has Swedish personnummer
+ * shape (lib/customers/personal-number-shape.ts). Legal-entity org numbers
+ * never match (month position >= 20), so an individual carrying a real
+ * organisationsnummer is left alone.
+ *
+ * Per row:
+ *   - personal_number NULL       -> personal_number = encrypt(org_number), org_number = NULL
+ *   - personal_number already set -> org_number = NULL only (the stored
+ *                                    personnummer wins; the duplicate is reported)
+ *
+ * Idempotent: a repaired row no longer matches the selection, and every
+ * update is guarded on the exact org_number value so a re-run or a concurrent
+ * edit can never double-apply. Safe to re-run.
+ *
+ * Usage:
+ *   npx tsx scripts/repair-customer-personal-number-in-org-number.ts            # dry run (read-only)
+ *   npx tsx scripts/repair-customer-personal-number-in-org-number.ts --confirm  # performs the writes
+ *   add --company <uuid> to limit either mode to one company
+ *
+ * Reads NEXT_PUBLIC_SUPABASE_URL + SUPABASE_SERVICE_ROLE_KEY from .env.local;
+ * --confirm additionally needs PERSONNUMMER_ENCRYPTION_KEY (the production
+ * key, same one the app encrypts with). Treat .env.local as pointing at
+ * PRODUCTION: the dry run is read-only; --confirm mutates PII. Never prints a
+ * personnummer; rows are reported by id and company.
+ */
+import { createClient } from '@supabase/supabase-js'
+import { config as dotenv } from 'dotenv'
+import { resolve } from 'node:path'
+import { encryptCustomerPersonalNumber } from '@/lib/customers/protect-personal-number'
+import {
+  normalizeReroutedPersonalNumber,
+  orgNumberHoldsPersonalNumber,
+} from '@/lib/customers/personal-number-shape'
+
+dotenv({ path: resolve(process.cwd(), '.env.local') })
+
+const SUPABASE_URL = process.env.NEXT_PUBLIC_SUPABASE_URL
+const SERVICE_KEY = process.env.SUPABASE_SERVICE_ROLE_KEY
+if (!SUPABASE_URL || !SERVICE_KEY) {
+  console.error('Missing NEXT_PUBLIC_SUPABASE_URL or SUPABASE_SERVICE_ROLE_KEY in .env.local')
+  process.exit(1)
+}
+const CONFIRM = process.argv.includes('--confirm')
+// Refuse to WRITE without the real key: encrypting with the dev fallback key
+// would make the values unreadable in production. The dry run encrypts
+// nothing, so it runs without it (the key lives in the Vercel env, not in
+// every local .env.local).
+if (CONFIRM && !process.env.PERSONNUMMER_ENCRYPTION_KEY) {
+  console.error(
+    'Missing PERSONNUMMER_ENCRYPTION_KEY. Refusing to write so rows are not encrypted with the dev fallback key '
+    + '(vercel env pull, or set it for this run).',
+  )
+  process.exit(1)
+}
+const companyFlag = process.argv.indexOf('--company')
+const ONLY_COMPANY = companyFlag >= 0 ? process.argv[companyFlag + 1] : undefined
+
+const sb = createClient(SUPABASE_URL, SERVICE_KEY, { auth: { persistSession: false } })
+
+type Row = {
+  id: string
+  company_id: string
+  customer_type: string
+  org_number: string | null
+  personal_number: string | null
+}
+
+async function main() {
+  const host = new URL(SUPABASE_URL!).host
+  console.log(
+    `Target: ${host}   mode: ${CONFIRM ? 'WRITE (--confirm)' : 'DRY RUN (read-only)'}`
+    + (ONLY_COMPANY ? `   company: ${ONLY_COMPANY}` : ''),
+  )
+
+  // Page on the PK: PostgREST caps an unranged select at 1000 rows.
+  const PAGE = 1000
+  const candidates: Row[] = []
+  for (let from = 0; ; from += PAGE) {
+    let query = sb
+      .from('customers')
+      .select('id, company_id, customer_type, org_number, personal_number')
+      .eq('customer_type', 'individual')
+      .not('org_number', 'is', null)
+      .order('id', { ascending: true })
+      .range(from, from + PAGE - 1)
+    if (ONLY_COMPANY) query = query.eq('company_id', ONLY_COMPANY)
+    const { data, error } = await query
+    if (error) throw new Error(`select customers: ${error.message}`)
+    const rows = (data ?? []) as Row[]
+    candidates.push(...rows)
+    if (rows.length < PAGE) break
+  }
+
+  const affected = candidates.filter((r) => orgNumberHoldsPersonalNumber(r.customer_type, r.org_number))
+  const toMove = affected.filter((r) => !r.personal_number)
+  const toClear = affected.filter((r) => r.personal_number)
+  const companies = new Set(affected.map((r) => r.company_id))
+
+  console.log(
+    `Individual rows with org_number: ${candidates.length}; personnummer-shaped: ${affected.length} `
+    + `across ${companies.size} companies (move: ${toMove.length}, clear-duplicate: ${toClear.length}).`,
+  )
+  for (const r of affected) {
+    console.log(`  ${r.personal_number ? 'CLEAR' : 'MOVE '}  customer ${r.id}  company ${r.company_id}`)
+  }
+
+  if (!CONFIRM) {
+    console.log('Dry run: no writes performed. Re-run with --confirm to apply.')
+    return
+  }
+
+  let moved = 0
+  let cleared = 0
+  let skipped = 0
+  for (const r of affected) {
+    // Guard on the exact current value: a concurrent edit or a re-run cannot
+    // double-apply, and a row that changed underneath is skipped, not clobbered.
+    // Two literal payloads rather than one built at runtime, so the
+    // no-phantom-columns scanner can resolve both.
+    const { data, error } = r.personal_number
+      ? await sb
+          .from('customers')
+          .update({ org_number: null })
+          .eq('id', r.id)
+          .eq('company_id', r.company_id)
+          .eq('org_number', r.org_number!)
+          .select('id')
+      : await sb
+          .from('customers')
+          .update({
+            org_number: null,
+            personal_number: encryptCustomerPersonalNumber(normalizeReroutedPersonalNumber(r.org_number!)),
+          })
+          .eq('id', r.id)
+          .eq('company_id', r.company_id)
+          .eq('org_number', r.org_number!)
+          .select('id')
+    if (error) {
+      console.error(`  FAILED customer ${r.id}: ${error.message}`)
+      continue
+    }
+    if (!data || data.length === 0) {
+      skipped += 1
+      continue
+    }
+    if (r.personal_number) cleared += 1
+    else moved += 1
+  }
+  console.log(`Done. moved: ${moved}, cleared duplicate org_number: ${cleared}, skipped (changed underneath): ${skipped}.`)
+}
+
+main().catch((err) => {
+  console.error(err instanceof Error ? err.message : err)
+  process.exit(1)
+})
diff --git a/skills/accounted-api/references/customers.md b/skills/accounted-api/references/customers.md
index 75535f75..2480c0f9 100644
--- a/skills/accounted-api/references/customers.md
+++ b/skills/accounted-api/references/customers.md
@@ -93,8 +93,8 @@ Creates a new customer for the company. Requires Idempotency-Key (UUID). Support
 **Pitfalls:**
 - Idempotency-Key is mandatory: calls without it return 400 VALIDATION_ERROR.
 - org_number uniqueness is enforced at the database level; duplicate inserts return 409 CUSTOMER_DUPLICATE_ORG_NUMBER.
-- For Swedish sole traders (customer_type=individual), org_number IS the personnummer. List responses mask it; the create endpoint accepts it as input.
-- An org_number shaped like a Swedish personnummer is rejected for business customer_types: create the customer as customer_type=individual (personal_number or org_number) so the number is masked and protected.
+- A personnummer-shaped org_number on customer_type=individual is treated as the personnummer submitted in the wrong field: it is stored encrypted as personal_number, returned masked (********-1234), and org_number is left empty. Prefer passing it as personal_number. Next to a different personal_number in the same body it is a 400.
+- An org_number shaped like a Swedish personnummer is rejected for business customer_types: create the customer as customer_type=individual with personal_number so the number is masked and protected.
 - personal_number is accepted only for customer_type=individual, stored encrypted, and returned in the masked form ********-1234.
 - If default_payment_terms is omitted, it defaults to the company setting invoice_default_days, falling back to 30.
 - VIES validation runs only on commit. Dry-run skips the external call and leaves vat_number_validated=false in the preview.
@@ -243,7 +243,7 @@ Patches the customer with the supplied fields. All fields optional. Idempotent (
 - org_number uniqueness is enforced at DB level: 23505 → 409 CUSTOMER_DUPLICATE_ORG_NUMBER.
 - VIES re-validation is best-effort and runs only on commit. A VIES timeout does not fail the update.
 - personal_number: a plaintext value is stored encrypted (individual customers only); the masked form a read returned (********-1234) means "leave unchanged" and is never stored; null clears it. Changing customer_type away from individual clears any stored personal_number.
-- An org_number shaped like a Swedish personnummer is rejected for business customer_types (400 CUSTOMER_ORG_NUMBER_IS_PERSONAL).
+- An org_number shaped like a Swedish personnummer is rejected for business customer_types (400 CUSTOMER_ORG_NUMBER_IS_PERSONAL). On an individual it is the personnummer in the wrong field: it is stored encrypted as personal_number and org_number is cleared; next to a different personal_number in the same body it is 400 CUSTOMER_PERSONAL_NUMBER_CONFLICT.
 
 | Parameter | In | Type | Required | Notes |
 |---|---|---|---|---|