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The ISO 20022 pain.001 salary payment file could never be generated: the route required company_settings.iban/bic, but no settings screen wrote those columns, so every request returned 400. The specific reason was also swallowed by getErrorMessage (isSwedishUserMessage did not know "krävs"/"saknar"), surfacing only the generic "Förfrågan innehåller ogiltiga uppgifter" (issue #945). - Add IBAN + BIC inputs to Settings > Fakturering > Bankuppgifter. BIC auto-derives from the clearing number / bank already entered, so in practice only the IBAN is typed. Validated client- and server-side. - Route requires the company IBAN (canonical debtor form every Swedish bank accepts) and derives the BIC, with clear actionable errors. - Employees are unchanged: domestic clearing + account (BBAN), which is what Swedish payroll collects. Only the company (debtor) uses IBAN. - getErrorMessage recognizes "krävs"/"saknar" so payment-file reasons surface instead of the generic 400. Fixes #945 Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>