Letter Before Action for an Unpaid Invoice

By ClaimKit UK Editorial Team · Updated February 2026

If a client has not paid your invoice, a pre-action letter is the final step before small claims. It sets out the contract, the work delivered, and the amount owed.

Summarize the work delivered

Describe the service provided and when it was completed or delivered. Reference the agreement, purchase order, or accepted quote.

State the payment terms

Include the invoice number, amount, due date, and any late payment terms that were agreed. Be clear on the total owed today.

Set a final deadline

Give a clear deadline to pay and explain that you will issue a small claim if payment is not received.

Keep evidence ready

If you proceed to a claim, you will need proof of the agreement, delivery, and non-payment. Gather these now to avoid delays.

Evidence checklist

Signed contract, PO, or accepted quote
Invoice showing due date and payment terms
Proof of delivery or completion
Emails or messages chasing payment
Any agreed late payment terms or interest

Common mistakes to avoid

Not including the invoice due date
Claiming interest without stating the basis
No proof that the work was delivered

FAQs

Can I charge late payment interest?

If your contract includes interest, or you are eligible under late payment legislation, you can include it. Keep the calculation clear.

Should I accept a payment plan?

If a payment plan is realistic, you can accept it. Put the terms in writing and keep a record of any missed payments.

What if the client disputes the work?

State your evidence and keep the letter factual. If the dispute continues, the court will decide based on the evidence.

Related guides

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