My client disputes my invoice. What happens next?
The short answer
The disputed part waits. The rest of the invoice is usually still due, and the late payment law counts a debt for any part of a price2, not only the whole, so interest starts the day after it was due3. Ask them in writing which item is wrong and what sum it covers, then ask for the undisputed part by a date. A court expects the other side to say which parts are disputed, and why8, so you are asking for nothing unusual.
England and Wales only. WolfX is software, not a law firm.
What you can add
A £5,000 invoice with £800 disputed
Say you invoiced another business £5,000, due on 31 August 2026. On 14 September they email: £800 of it is wrong, and they will pay nothing until it is sorted. The other £4,200 is not in question. On 30 September it is still unpaid: 30 days late. Interest started on 1 September, so the rate is set by the Bank Rate on 30 June 2026: 3.75%6 plus 8%5, or 11.75%.
- The invoice£5,000.00
- Less the part they dispute−£800.00
- Interest: £4,200 × 11.75% ÷ 365 × 30 days5£40.56
- Fixed sum (debts from £1,000 to £9,999.99)7£70.00
- Not in dispute, owed on 30 September 2026£4,310.56
Interest adds £1.35 a day from here, until the £4,200 is paid. The £800 waits. If it proves to be owed, interest usually counts3 from the same due date.
The road ahead
Six steps, before any court claim.
Step 1: Check their complaint against your record
Before you reply, lay their points beside the order, the brief, the sign-offs and the emails. Note what was agreed, what was delivered and what they approved. If they are partly right, you will know before they say so.
Step 2: Ask in writing what is wrong, and for the rest
Send the letter below by email. It asks which item they dispute, what is wrong, what sum it covers and what they want done, and for the rest by a date. A promise to pay "when it is sorted" is not a date.
The Act starts interest the day after the due date3, and a later complaint is not on its list of things that move that day. Work the interest out to the day before you write again.
Step 3: Answer the complaint in full
When their details arrive, reply to each point calmly, with your paperwork. Where they are right, say so and offer the fix.
A credit note cuts your own invoice. Issue one only for a sum you have agreed in writing, not to keep the peace.
Step 4: Offer to talk the disputed part through
Offer a call or a meeting, and email a note of what was said. Before you put an offer to compromise in writing, read what "without prejudice" means.
If your client is a larger business, the Small Business Commissioner may be able to help with a payment dispute you cannot resolve12. The service is free and confidential.
Step 5: Suggest mediation if talks stall
A mediator is a neutral person who helps both sides agree. The court's rules ask you to consider mediation or another way to settle8 before a claim. If they suggest it, answer: silence or a refusal could lead a court to order extra costs8.
Under a pilot that runs to 6 April 202710, a court claim of £10,000 or less that they defend usually goes to a free mediation call arranged by the court11.
Step 6: Then send a letter before action for that part
Write a letter before action for the undisputed sum. If they have still named no item or sum, ask for the whole invoice: your emails show you asked.
A company should reply within 14 days8 in a straightforward case. A sole trader has 309.
A letter you can copy
Reply to a dispute: ask what is wrong, claim the rest
Send it the day their dispute arrives, once you have read their complaint against your own record.
Tap a highlighted gap to see what goes in it.
Send it by email so it is dated, and keep a copy with the invoice and their complaint. If they only ring, email a note of the call. Work the undisputed sum from what they have said, not from what you suspect: the invoice less the sum they say is affected. If they have named no item or sum, send only the four questions and the date, and ask for payment in your next letter.
When not to bother
When it isn't worth it
- They are a consumer, or you are outside England and Wales. The late payment law only covers sales between businesses1. Consumer sales follow other rules, and Scotland and Northern Ireland have their own courts.
- Their complaint is right. Fix it, send a corrected invoice and ask for payment of that. If your own mistake caused the delay, a court can cut the interest for that period4.
- The disputed sum is small and the client is worth keeping. Agree a figure in writing, issue a credit note for that figure only, and move on. Get the undisputed part paid first.
- They dispute all of it. There is no undisputed part to claim yet. Ask for their reasons in writing, gather your own record of what was ordered, delivered and signed off, and try mediation before a claim.
- Your contract ties payment to a sign-off that has not happened. The due date may not have arrived: an agreed date can depend on an event3. Read the clause before you ask for money.
The Wolf's note
A dispute becomes useful the moment it has a number. Ask for theirs in writing: which item, what sum. Everything outside that sum is usually due already, and earning interest.
Mr. Wolf · the AI inside WolfX
What comes next
Your next move
My client says the work wasn't good enough and won't pay. Can they do that?
Only for the part that is really wrong.
7 min read · Letter included
My client says they didn't authorise the extra work. Can I charge for it?
Yes, if they asked for it, or watched it done and let it go on.
Put it in writing
What is a letter before action, and how do I write one?
A formal last letter before a court claim, and you can write it yourself.
7 min read · Letter included
Don't want to do this yourself?
The Wolf does every step for you. He works out the sums, writes the letters and keeps track of every date. Nothing goes without your yes.