diff --git a/supabase/migrations/20260516130000_seed_chart_of_accounts_restore_swedish_chars.sql b/supabase/migrations/20260516130000_seed_chart_of_accounts_restore_swedish_chars.sql
new file mode 100644
index 00000000..8399a976
--- /dev/null
+++ b/supabase/migrations/20260516130000_seed_chart_of_accounts_restore_swedish_chars.sql
@@ -0,0 +1,144 @@
+-- Restore Swedish characters (å/ä/ö/Å/Ä/Ö) in seed_chart_of_accounts and
+-- populate sru_code from BAS 2026 reference data. Previously the account
+-- names were inserted as ASCII-folded literals (e.g. 'Arets resultat'),
+-- which left every newly-created company with chart-of-accounts rows
+-- missing diacritics. SIE-imported accounts were unaffected because that
+-- path reads names from lib/bookkeeping/bas-data/.
+--
+-- SRU codes are populated from lib/bookkeeping/bas-data/ so the seeded
+-- chart can produce valid SRU/INK2 filings for users who never import a
+-- SIE file.
+--
+-- This migration only changes the function definition. Existing companies
+-- with broken seed rows are intentionally NOT backfilled here.
+
+DROP FUNCTION IF EXISTS public.seed_chart_of_accounts(uuid, text);
+
+CREATE OR REPLACE FUNCTION public.seed_chart_of_accounts(p_company_id uuid, p_entity_type text)
+RETURNS void
+LANGUAGE plpgsql
+SECURITY DEFINER
+SET search_path = public
+AS $$
+DECLARE
+  v_account_count integer;
+  v_user_id uuid;
+BEGIN
+  SELECT created_by INTO v_user_id FROM public.companies WHERE id = p_company_id;
+
+  SELECT count(*) INTO v_account_count
+  FROM public.chart_of_accounts
+  WHERE company_id = p_company_id;
+
+  IF v_account_count > 0 THEN
+    RETURN;
+  END IF;
+
+  -- Assets (1xxx)
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '1510', 'Kundfordringar', 1, '15', 'asset', 'debit', 'k1', true, '7211'),
+    (v_user_id, p_company_id, '1910', 'Kassa', 1, '19', 'asset', 'debit', 'k1', true, '7212'),
+    (v_user_id, p_company_id, '1930', 'Företagskonto / checkkonto', 1, '19', 'asset', 'debit', 'k1', true, '7212'),
+    (v_user_id, p_company_id, '1940', 'Övriga bankkonton', 1, '19', 'asset', 'debit', 'k1', true, '7212');
+
+  -- Equity (2xxx)
+  IF p_entity_type = 'enskild_firma' THEN
+    -- Enskild firma equity accounts: sru_code intentionally NULL.
+    -- BAS reference maps these to INK2 SRU 7221 ("Övrigt eget kapital"),
+    -- which is the aktiebolag tax form. EF entities file NE-bilaga, not
+    -- INK2, and owner drawings/contributions on 2013/2018 must not be
+    -- reported as balance-sheet equity by SIE/INK2 consumers.
+    INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+    VALUES
+      (v_user_id, p_company_id, '2010', 'Eget kapital', 2, '20', 'equity', 'credit', 'k1', true, NULL),
+      (v_user_id, p_company_id, '2013', 'Övriga egna uttag', 2, '20', 'equity', 'credit', 'k1', true, NULL),
+      (v_user_id, p_company_id, '2018', 'Övriga egna insättningar', 2, '20', 'equity', 'credit', 'k1', true, NULL);
+  END IF;
+
+  IF p_entity_type = 'aktiebolag' THEN
+    INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+    VALUES
+      (v_user_id, p_company_id, '2081', 'Aktiekapital', 2, '20', 'equity', 'credit', 'k1', true, '7220'),
+      (v_user_id, p_company_id, '2091', 'Balanserat resultat', 2, '20', 'equity', 'credit', 'k1', true, '7221'),
+      (v_user_id, p_company_id, '2099', 'Årets resultat', 2, '20', 'equity', 'credit', 'k1', true, '7222');
+  END IF;
+
+  -- Liabilities (2xxx) — BAS 2026 VAT account labels
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '2440', 'Leverantörsskulder', 2, '24', 'liability', 'credit', 'k1', true, '7230'),
+    (v_user_id, p_company_id, '2611', 'Utgående moms försäljning inom Sverige, 25%', 2, '26', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2621', 'Utgående moms försäljning inom Sverige, 12%', 2, '26', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2631', 'Utgående moms försäljning inom Sverige,  6%', 2, '26', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2641', 'Debiterad ingående moms', 2, '26', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2650', 'Redovisningskonto för moms', 2, '26', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2710', 'Personalskatt', 2, '27', 'liability', 'credit', 'k1', true, '7231'),
+    (v_user_id, p_company_id, '2731', 'Avräkning socialavgifter', 2, '27', 'liability', 'credit', 'k1', true, '7231');
+
+  IF p_entity_type = 'aktiebolag' THEN
+    INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+    VALUES
+      (v_user_id, p_company_id, '2893', 'Skuld till aktieägare', 2, '28', 'liability', 'credit', 'k1', true, '7231');
+  END IF;
+
+  -- Revenue (3xxx)
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '3001', 'Försäljning tjänster 25%', 3, '30', 'revenue', 'credit', 'k1', true, '7310'),
+    (v_user_id, p_company_id, '3002', 'Försäljning varor 25%', 3, '30', 'revenue', 'credit', 'k1', true, '7310'),
+    (v_user_id, p_company_id, '3100', 'Momsfri försäljning', 3, '31', 'revenue', 'credit', 'k1', true, '7311'),
+    (v_user_id, p_company_id, '3900', 'Övriga rörelseintäkter', 3, '39', 'revenue', 'credit', 'k1', true, '7311'),
+    (v_user_id, p_company_id, '3960', 'Valutakursvinster', 3, '39', 'revenue', 'credit', 'k1', true, '7310');
+
+  -- COGS (4xxx)
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '4000', 'Varuinköp', 4, '40', 'expense', 'debit', 'k1', true, '7320');
+
+  -- External expenses (5xxx-6xxx)
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '5010', 'Lokalhyra', 5, '50', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '5410', 'Förbrukningsinventarier', 5, '54', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '5420', 'Programvaror', 5, '54', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '5460', 'Förbrukningsmaterial', 5, '54', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '5800', 'Resekostnader', 5, '58', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '5910', 'Annonsering', 5, '59', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6071', 'Representation avdragsgill', 6, '60', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6110', 'Kontorsmateriel', 6, '61', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6212', 'Mobiltelefon', 6, '62', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6230', 'Datakommunikation', 6, '62', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6530', 'Redovisningstjänster', 6, '65', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6570', 'Bankavgifter', 6, '65', 'expense', 'debit', 'k1', true, '7321'),
+    (v_user_id, p_company_id, '6991', 'Övriga avdragsgilla kostnader', 6, '69', 'expense', 'debit', 'k1', true, '7330');
+
+  -- Personnel (7xxx)
+  IF p_entity_type = 'aktiebolag' THEN
+    INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+    VALUES
+      (v_user_id, p_company_id, '7010', 'Löner', 7, '70', 'expense', 'debit', 'k1', true, '7322'),
+      (v_user_id, p_company_id, '7210', 'Semesterlöner', 7, '72', 'expense', 'debit', 'k1', true, '7322'),
+      (v_user_id, p_company_id, '7510', 'Arbetsgivaravgifter', 7, '75', 'expense', 'debit', 'k1', true, '7322');
+  END IF;
+
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '7960', 'Valutakursförluster', 7, '79', 'expense', 'debit', 'k1', true, '7360');
+
+  -- Financial (8xxx)
+  INSERT INTO public.chart_of_accounts (user_id, company_id, account_number, account_name, account_class, account_group, account_type, normal_balance, plan_type, is_system_account, sru_code)
+  VALUES
+    (v_user_id, p_company_id, '8310', 'Ränteintäkter', 8, '83', 'revenue', 'credit', 'k1', true, '7313'),
+    (v_user_id, p_company_id, '8410', 'Räntekostnader', 8, '84', 'expense', 'debit', 'k1', true, '7323');
+END;
+$$;
+
+-- Restore the EXECUTE grant. Each prior DROP/CREATE has silently dropped
+-- the grant originally established in 20240101000009; SECURITY DEFINER
+-- callers via service role still work, but RPC calls from the
+-- authenticated role have been failing with permission errors since
+-- 20260330130000. Match the original grant from migration 009.
+GRANT EXECUTE ON FUNCTION public.seed_chart_of_accounts(uuid, text) TO authenticated;
+
+NOTIFY pgrst, 'reload schema';
diff --git a/supabase/migrations/__tests__/seed-chart-of-accounts.pg.test.ts b/supabase/migrations/__tests__/seed-chart-of-accounts.pg.test.ts
index 5b608f23..7caa4fbc 100644
--- a/supabase/migrations/__tests__/seed-chart-of-accounts.pg.test.ts
+++ b/supabase/migrations/__tests__/seed-chart-of-accounts.pg.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { seedCompany } from '@/tests/pg/fixtures'
+import { insertAuthUser, insertCompany, seedCompany } from '@/tests/pg/fixtures'
 import { getPool } from '@/tests/pg/setup'
 
 /**
@@ -11,8 +11,40 @@ import { getPool } from '@/tests/pg/setup'
  * the VAT-rutor mapping both route by account number, so a mislabel in this
  * function never breaks any other test — only the chart-of-accounts UI shows
  * the wrong text. This test is the canary.
+ *
+ * The diacritic + SRU groups below cover the 2026-05-16 migration that
+ * restored å/ä/ö in account names and started populating sru_code from BAS
+ * reference. Both are bytes-on-disk concerns the engine never reads but the
+ * UI and tax-filing exports do.
  */
 
+interface AccountRow {
+  account_number: string
+  account_name: string
+  sru_code: string | null
+}
+
+async function callSeed(
+  companyId: string,
+  entityType: 'aktiebolag' | 'enskild_firma',
+): Promise<void> {
+  await getPool().query(
+    `SELECT public.seed_chart_of_accounts($1::uuid, $2::text)`,
+    [companyId, entityType],
+  )
+}
+
+async function getAccounts(companyId: string): Promise<AccountRow[]> {
+  const res = await getPool().query<AccountRow>(
+    `SELECT account_number, account_name, sru_code
+       FROM public.chart_of_accounts
+      WHERE company_id = $1
+      ORDER BY account_number`,
+    [companyId],
+  )
+  return res.rows
+}
+
 describe('seed_chart_of_accounts', () => {
   it('seeds 26xx VAT accounts with BAS-correct labels', async () => {
     const { companyId } = await seedCompany()
@@ -64,3 +96,164 @@ describe('seed_chart_of_accounts', () => {
     expect(rows[0].account_name).toMatch(/[Ii]ng.*moms/)
   })
 })
+
+describe('seed_chart_of_accounts — Swedish characters', () => {
+  it('inserts Swedish-character account names byte-for-byte for aktiebolag', async () => {
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const byNum = new Map((await getAccounts(companyId)).map((r) => [r.account_number, r]))
+
+    // Spot-check every row whose name contains å/ä/ö/Å/Ä/Ö. If diacritics
+    // were stripped during insertion these assertions are the ones that
+    // would fail.
+    const expected: Record<string, string> = {
+      '1930': 'Företagskonto / checkkonto',
+      '1940': 'Övriga bankkonton',
+      '2099': 'Årets resultat',
+      '2440': 'Leverantörsskulder',
+      '2611': 'Utgående moms försäljning inom Sverige, 25%',
+      '2621': 'Utgående moms försäljning inom Sverige, 12%',
+      '2631': 'Utgående moms försäljning inom Sverige,  6%',
+      '2641': 'Debiterad ingående moms',
+      '2650': 'Redovisningskonto för moms',
+      '2731': 'Avräkning socialavgifter',
+      '2893': 'Skuld till aktieägare',
+      '3001': 'Försäljning tjänster 25%',
+      '3002': 'Försäljning varor 25%',
+      '3100': 'Momsfri försäljning',
+      '3900': 'Övriga rörelseintäkter',
+      '4000': 'Varuinköp',
+      '5410': 'Förbrukningsinventarier',
+      '5460': 'Förbrukningsmaterial',
+      '6530': 'Redovisningstjänster',
+      '6991': 'Övriga avdragsgilla kostnader',
+      '7010': 'Löner',
+      '7210': 'Semesterlöner',
+      '7960': 'Valutakursförluster',
+      '8310': 'Ränteintäkter',
+      '8410': 'Räntekostnader',
+    }
+
+    for (const [num, name] of Object.entries(expected)) {
+      const row = byNum.get(num)
+      expect(row, `account ${num} should be seeded`).toBeDefined()
+      expect(row!.account_name, `account ${num} name`).toBe(name)
+    }
+  })
+
+  it('inserts Swedish-character account names for enskild_firma equity accounts', async () => {
+    // seedCompany() defaults to aktiebolag, so go direct for the EF case.
+    const userId = await insertAuthUser()
+    const companyId = await insertCompany({ createdBy: userId, entityType: 'enskild_firma' })
+    await callSeed(companyId, 'enskild_firma')
+    const byNum = new Map((await getAccounts(companyId)).map((r) => [r.account_number, r]))
+
+    expect(byNum.get('2013')?.account_name).toBe('Övriga egna uttag')
+    expect(byNum.get('2018')?.account_name).toBe('Övriga egna insättningar')
+
+    // AB-only equity accounts must not appear for enskild_firma.
+    expect(byNum.has('2081')).toBe(false)
+    expect(byNum.has('2091')).toBe(false)
+    expect(byNum.has('2099')).toBe(false)
+
+    // EF equity accounts must NOT carry the AB-oriented INK2 SRU code 7221.
+    // EF entities file NE-bilaga instead of INK2; emitting `#SRU 2013 7221`
+    // in a SIE export would steer downstream tax software to report owner
+    // drawings as balance-sheet equity, which is wrong for sole traders.
+    expect(byNum.get('2010')?.sru_code).toBeNull()
+    expect(byNum.get('2013')?.sru_code).toBeNull()
+    expect(byNum.get('2018')?.sru_code).toBeNull()
+  })
+
+  it('stores diacritics as multi-byte UTF-8, not as ASCII folds', async () => {
+    // octet_length > char_length holds only when the string contains
+    // multi-byte UTF-8 code units. If a future regression strips å/ä/ö
+    // again the lengths would become equal and this fails loudly.
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const res = await getPool().query<{
+      account_number: string
+      octets: number
+      chars: number
+    }>(
+      `SELECT account_number,
+              octet_length(account_name) AS octets,
+              char_length(account_name)  AS chars
+         FROM public.chart_of_accounts
+        WHERE company_id = $1
+          AND account_number IN ('2099', '2440', '2611', '2731', '7010', '8410')`,
+      [companyId],
+    )
+    expect(res.rows.length).toBe(6)
+    for (const row of res.rows) {
+      expect(
+        row.octets,
+        `account ${row.account_number}: octet_length must exceed char_length`,
+      ).toBeGreaterThan(row.chars)
+    }
+  })
+})
+
+describe('seed_chart_of_accounts — SRU codes', () => {
+  it('populates sru_code for every seeded account so the K1 chart can produce SRU/INK2 filings', async () => {
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const rows = await getAccounts(companyId)
+
+    const missing = rows.filter((r) => r.sru_code === null)
+    expect(
+      missing,
+      `every seeded row must have sru_code populated. Missing: ${missing
+        .map((r) => `${r.account_number} (${r.account_name})`)
+        .join(', ')}`,
+    ).toHaveLength(0)
+  })
+
+  it('maps representative accounts to the SRU codes from BAS reference', async () => {
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const byNum = new Map((await getAccounts(companyId)).map((r) => [r.account_number, r]))
+
+    // Spot-check values pulled from lib/bookkeeping/bas-data/. These three
+    // map to Skatteverket SRU fields in INK2; getting them wrong would
+    // silently break tax filing.
+    expect(byNum.get('2099')?.sru_code).toBe('7222')
+    expect(byNum.get('2611')?.sru_code).toBe('7231')
+    expect(byNum.get('2731')?.sru_code).toBe('7231')
+    expect(byNum.get('1930')?.sru_code).toBe('7212')
+    expect(byNum.get('3001')?.sru_code).toBe('7310')
+    expect(byNum.get('7010')?.sru_code).toBe('7322')
+  })
+})
+
+describe('seed_chart_of_accounts — invariants', () => {
+  it('is idempotent: a second call on a company that already has accounts is a no-op', async () => {
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const firstCount = (await getAccounts(companyId)).length
+
+    await callSeed(companyId, 'aktiebolag')
+    const secondCount = (await getAccounts(companyId)).length
+
+    expect(secondCount).toBe(firstCount)
+  })
+
+  it('seeds plan_type=k1 and is_system_account=true on every starter account', async () => {
+    // These two flags are what the SIE importer's existing-account
+    // short-circuit relies on to distinguish seeded rows from imported
+    // ones. Drifting away from them would change the importer's
+    // behaviour for existing companies silently.
+    const { companyId } = await seedCompany()
+    await callSeed(companyId, 'aktiebolag')
+    const res = await getPool().query<{ bad_plan: number; bad_flag: number }>(
+      `SELECT
+         count(*) FILTER (WHERE plan_type IS DISTINCT FROM 'k1')::int      AS bad_plan,
+         count(*) FILTER (WHERE is_system_account IS DISTINCT FROM true)::int AS bad_flag
+       FROM public.chart_of_accounts
+       WHERE company_id = $1`,
+      [companyId],
+    )
+    expect(res.rows[0]!.bad_plan).toBe(0)
+    expect(res.rows[0]!.bad_flag).toBe(0)
+  })
+})