How to Write a Complaint Letter in the UK
A well-written complaint letter is often the fastest route to a resolution. This guide explains what to include, who to write to, and what to do if you are ignored.
When should you write a complaint letter?
Write a formal complaint letter when informal attempts to resolve an issue have failed — for example after a phone call or in-store complaint that went nowhere. A written complaint creates a dated paper trail, signals seriousness, and is often required before you can escalate to a regulator or ombudsman.
Common situations include: faulty goods or services, billing errors, poor treatment by a company or council, NHS care concerns, landlord failures, and disputes with utility providers.
What UK law supports your complaint?
- —Consumer Rights Act 2015 — goods must be of satisfactory quality, fit for purpose, and as described
- —Consumer Contracts Regulations 2013 — additional protections for online and distance purchases
- —Supply of Goods and Services Act 1982 — services must be carried out with reasonable care and skill
- —Financial Services and Markets Act 2000 — complaints about financial firms can be escalated to the FOS
What to include in your complaint letter
- —Your full name, address, and contact details
- —The date and a clear reference to any previous correspondence
- —A factual, chronological account of what happened
- —The specific resolution you want — refund, repair, replacement, apology, or explanation
- —A clear deadline for response — 14 days is standard
- —A statement that you will escalate if no satisfactory response is received
Keep the tone professional and factual. Avoid emotional language — a calm, specific letter is far more effective than an angry one, and puts you in a stronger position if you need to escalate.
Who to escalate to if the company ignores you
- —Financial services: Financial Ombudsman Service (FOS) at financial-ombudsman.org.uk
- —Energy: Ombudsman Services: Energy at ombudsman-services.org
- —Telecoms: Ombudsman Services: Communications
- —Retail / goods: Trading Standards or Citizens Advice
- —NHS: Parliamentary and Health Service Ombudsman (PHSO)
- —Council: Local Government and Social Care Ombudsman
What about small claims court?
If a company owes you money and refuses to pay, you can issue a claim through the County Court. For amounts under £10,000, the Small Claims Track applies — it is designed to be used without a solicitor. Issue claims online via Money Claim Online at moneyclaim.service.gov.uk. You must send a pre-action letter before issuing a claim.
How long does the company have to respond?
There is no universal legal deadline, but best practice and most regulatory codes expect a full response within 8 weeks. For financial firms, the FCA requires a response within 8 weeks before the FOS will accept a referral. For NHS complaints, the expectation is 40 working days.