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Letter before action for unpaid building work

By Alex Williams, director of Ty Parc Construction, a building contractor in Newport, South Wales · Last reviewed 21 October 2026

A letter before action is the formal final demand you send before taking a client to court for money they owe you. In England and Wales, a court expects you to send one, and if the client is a homeowner or sole trader you must follow the Pre-Action Protocol for Debt Claims: include the amount, how it’s made up, how to pay, and give them 30 days to reply. Use the free generator below to write yours in a few minutes.

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Before you send one

  • Check you’re owed it: the invoice matches the price you agreed, plus extras the client agreed to, minus anything taken out. If an extra was never agreed in writing, expect the client to dispute it.
  • Send a polite reminder and a final reminder first, and keep copies.
  • Ask what’s wrong. A lot of “won’t pay” is really “doesn’t agree with the final figure”. If the client says the work is defective or unfinished, it’s a dispute about the work, not just a debt — see “If the client disputes the work” below.

Which rules apply

ClientRulesTime to reply
A homeowner or other individual (including a sole trader)Pre-Action Protocol for Debt Claims — enclose the protocol’s Information Sheet, Reply Form and Financial Statement30 days from the date of the letter
A company or partnershipPractice Direction – Pre-Action Conduct (be reasonable and proportionate)Usually 14 days

If the client disputes the quality of the work or says it isn’t finished, the Pre-Action Protocol for Construction and Engineering Disputes may apply instead, which has its own steps. Take advice before you go further.

What your letter must say

  1. Your business name and address, and the client’s.
  2. What the work was, the site address and when it was done.
  3. The agreement: the date of the quote or contract, the price, and any extras agreed — and say you’ll send copies.
  4. Each invoice: number, date, amount, what’s been paid, what’s outstanding.
  5. Interest you’re claiming (see below) and whether it’s still adding up.
  6. How to pay — bank details and the reference to use.
  7. The deadline, as a date.
  8. That you’ll start court proceedings without further notice if it isn’t paid or answered by then.
  9. For individuals: the protocol’s Information Sheet, Reply Form and Financial Statement enclosed.

Date the letter and post it that day or the next; you can email a copy too.

Interest you can claim

  • From a homeowner or individual: simple interest at 8% a year on the unpaid amount from when it was due, if you go to court (County Courts Act 1984, section 69), unless your contract sets a different rate.
  • From a business: statutory interest at 8% above the Bank of England base rate, plus fixed compensation of £40 (debts under £1,000), £70 (£1,000 to £9,999.99) or £100 (£10,000 or more), under the Late Payment of Commercial Debts (Interest) Act 1998.

Example — figures are illustrative

An invoice of £4,800 due on 1 August, still unpaid on 21 October: 81 days × £4,800 × 8% ÷ 365 = £85.22 interest so far, then £1.05 a day.

If they don’t reply or pay

Claims up to £10,000 normally go to the small claims track. You can claim online on GOV.UK (“Make a court claim for money”). The issue fee depends on the amount — from £35 for claims up to £300 to £455 for claims between £5,000.01 and £10,000 (fees as published July 2026; check GOV.UK form EX50 for current fees). If the client responds and you still can’t agree, give them at least 14 days’ notice before you issue.

If the client disputes the work

List the specific issues they raise, offer to inspect and put right any genuine defects, keep dated photos, and consider mediation before court.

For work on someone’s own home, the Construction Act’s payment notice and adjudication rules may not apply (the “residential occupier” exception — the Court of Appeal looked at it in RBH Building Contractors Ltd v James [2026] EWCA Civ 511), so don’t rely on “they didn’t send a pay less notice” with homeowners. Get advice.

Stop it happening on the next job

Most chasing letters come down to one thing: the client and builder remember a different final figure. Agree the price, every extra and every payment in writing as you go, and the final invoice is just the sum of things both of you already signed off. Our guide to JCT, FMB and simple building contracts covers what to put in writing at the start.

Official sources