United Kingdom
- Complaint to the bank — Immediately, in writing. For payment services the bank must give a final response within 15 business days (35 in exceptional cases).
- Financial Ombudsman Service — After the final response or once the deadline passes, within 6 months. Free for consumers and small businesses; the client or a representative files.
- Data subject access request — In parallel. Under UK GDPR the bank answers within a month; often the only way to learn the real grounds.
Deadlines: From 28 April 2026 the bank gives consumers and micro-enterprises 90 days and detailed reasons on new contracts; older contracts get 2 months. Exception: suspected financial crime. Final response to a payment complaint: 15 business days. Ombudsman filing: within 6 months of it.