My client says they didn't authorise the extra work. Can I charge for it?
The short answer
Yes, if they asked. Under general contract law, asking for more work, even in a call, usually means they will pay for it, and a client who sees the extra done, knows it is extra and lets it go on can be treated the same way. If nothing in your contract or past dealings sets the price, the law adds a reasonable charge1, so an unpriced extra is not a free one. Send the extras on their own invoice, so a row over them cannot hold up the main one.
England and Wales only. WolfX is software, not a law firm.
What you can add
A £2,400 extras invoice, 22 days late
Say you made a £7,500 brand film for another business, and that invoice was paid on time. Before delivery they emailed twice, on 27 July and 3 August 2026, asking for two more edit rounds and a cut-down for social media. Your quote set £600 a day for work outside the brief, and the extras took 4 days. You delivered on 14 August and invoiced the extras on their own on 17 August. Your quote gave 30 days after the invoice date: due 16 September. On 8 October it is unpaid: 22 days late. Interest started on 17 September, so the rate is set by the Bank Rate on 30 June 2026: 3.75%7 plus 8%6, or 11.75%.
Then it grows by 77p a day until they pay. The late payment law counts a debt for any part of a price3, so the extras invoice earns its own interest and fixed sum, and the fixed sum is charged once for each late payment5. This sum rests on a rate already in your quote. If no price had been named, the same law still applies to your reasonable charge: interest usually runs from 17 September4 on whatever is agreed or decided, and the fixed sum is added too.
The road ahead
Seven steps. Free unless you need a solicitor or a court.
Step 1: Find the message that asked
Find the email, text or call note where they asked, and any dated draft or reply showing they knew it was extra. A spoken request counts but is harder to show. Check your quote: what it covered is not an extra. What proof you need has its own page.
Steps 1 and 2 come from how courts decide these cases, not from an Act.
Step 2: Check who asked, and what your contract says
They will say whoever asked could not spend. Point to whoever approves the budget: did they see the extra or its result and say nothing, or pay for earlier extras the same way? Silence is not a signature, but a court can weigh it.
Some contracts have a variation clause: changes must be written or signed, which can matter. On a large sum, see a solicitor who does contract disputes.
Step 3: Price each extra
An agreed price is the price, even one in a text. A rate in your contract, or one set by how you have billed each other before, is too1. Only if none fixes it does the law add a reasonable charge, which is a question of fact1.
Your quoted rate is the best yardstick. Pricing the extras after the event at more than that rate hands them the argument.
Step 4: Invoice the extras on their own
Give the extras their own invoice and due date, one line each: date asked, days or units, rate.
Send it promptly. With no date agreed, the 30 days usually begin with the later of the day the work is done and the day they have notice of the sum4. On building work with no dates, the Scheme for Construction Contracts9 puts the due date no earlier than your written claim.
Step 5: Send the email below
Send it to the person who approves the budget. It follows what the court's rules ask of a first letter: the basis of the claim, the facts, what you want and how the amount is worked out8.
Give them 14 days, a reasonable time to reply in a straightforward case8. They may pay, name an item and say why, or say nothing. If they name one, see a disputed invoice.
Step 6: Still unpaid? Send a letter before action
Treat the extras like any late invoice and send a letter before action for them alone; that page covers sole traders. A claim for £10,000 or less is normally a small claim10, and the route to court is on its own page.
Step 7: Next job, agree each extra in two lines
Before an extra starts, email two lines: “Extra: two more edit rounds. Price: £600 a day, about 2 days. OK to go ahead?” A reply of “yes” is a dated record.
A charge first met on the final invoice is the one they can say was not agreed.
A letter you can copy
Email asking them to confirm and pay for the extra work
Send it once the extras invoice is overdue and they say they did not authorise the work, or say nothing. Send it apart from any chase of the main invoice.
Tap a highlighted gap to see what goes in it.
Send it by email to the person who approves the budget, and copy the person who asked. Attach the invoice and the messages, so the email is a dated record. Send it on its own, not as a reply to a chase of the main invoice, so the two stay apart. Do not mark it “without prejudice”. You want to be able to show it to a court later.
When not to bother
When it isn't worth it
- They're a consumer, or you're outside England and Wales. The late payment law covers only sales between businesses2, and consumer contracts follow other rules. Scotland and Northern Ireland have their own courts. This page stops there.
- You offered it, or your quote already covered it. Work they did not ask for is hard to bill: they cannot have agreed to pay for something they did not know was extra. Absorb it, and ask first next time.
- The only proof is a call nobody wrote down. It is your word against theirs. Email them a note of what was agreed on the call, dated today, and see whether they correct it. If they do, you learn what the argument is.
- The extra is small and the client is worth keeping. Absorb it once, say in writing that it is a one-off, and use the two-line note from step 7 before the next one.
- Your contract says changes must be signed, and these were not. Such a clause can matter. On a large sum, have a solicitor who does contract disputes read it before you send anything stronger than the email.
The Wolf's note
If the work was asked for, what is missing is one page that says so: who asked, when, at what rate. Build it from the messages you already have, and send it with the invoice. The next extra starts with two lines in writing.
Mr. Wolf · the AI inside WolfX
What comes next
Your next move
No written contract: can I still get paid?
Yes. A verbal agreement is a contract.
6 min read · Letter included
My client disputes my invoice. What happens next?
The disputed part waits.
6 min read · Letter included
What proof do I need to show I did the work and they owe me?
Proof is five kinds of paper: the deal, the work, their acceptance, your invoice and your chasing.
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.