The one rule: price it before you do it
If the client asks for something that was not in the quote, or you find something that changes the job, stop and price it before you start. Not at the end, not on the final invoice. A price agreed in advance is very hard to argue with; a surprise line at the end is easy to argue with.
Legally you can usually still charge a reasonable amount for work a client asked for, even without a written price. But "reasonable" is something you may have to prove, and that is slow and stressful. Agreeing it first saves the whole fight.
Get the yes in writing
A verbal "yeah, go on" in the kitchen is worth very little three weeks later. You want a written record with four things in it:
- What the extra work is, in plain words
- Why it is needed (the client asked, or what you found)
- The price, or the day rate and a fair estimate of days
- The client agreeing to it, with a date
A text or email reply that says "yes, go ahead at £450" is far better than nothing. A signed approval on the client's phone is better still.
Send each extra to the client with photos and a price. They approve it on their phone.
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Take photos of what you found
When the extra comes from something you uncovered - rot behind the tiles, a joist cut through, old wiring - photograph it before you fix it. Once it is covered up, the only evidence is your word. Two or three photos with the date on them end most arguments before they start.
Keep extras separate from the original quote
Do not quietly fold extra work into the main price. List each extra separately with its own price and approval. At the end, the final invoice reads: original quote, plus these approved extras, less payments. The client can tick each one off.
If the client will not pay for the extras
- Invoice the original quoted work and the extras as separate lines, so the undisputed part gets paid.
- Do not accept a part payment "in full and final settlement" unless you mean it.
- Send copies of the written approvals and the photos.
- If it still is not paid, follow the steps in what to do when a client will not pay.
Small extras matter as much as big ones. Five £80 "while you're here" jobs is £400 you will not see without a record.
General information for England and Wales, not legal or tax advice. For your own situation, speak to a solicitor, accountant or Citizens Advice.