How to Handle Variations and Extras
Written by James Walker · Last reviewed 16 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
The short answer
- Unpriced extras are the single biggest cause of disputed final bills in domestic work.
- Price every variation in writing before doing it. A text message is enough.
- If they will not agree a price, do not do the work.
- Say whether it changes the completion date.
- Twenty small unpriced favours become one large argument at the end.
On this page
How it happens
Never through dishonesty. It happens like this:
The customer asks for an extra socket while you are there. You do it, it takes ten minutes and refusing feels petty. Nobody mentions money.
Repeat across a four-month job. At the end you produce a final invoice with extras on it, and from their side it looks like a price increase they never agreed to. From your side it is work you did for free unless they accept the charge.
Both of you are being reasonable. The system was wrong.
The ten-second habit
Before doing anything outside the quote, send a message:
"That's another £180 including materials, and it'll add half a day. Happy to go ahead?"
Ten seconds. It removes the argument entirely, and customers almost never object, because the point at which they object is when it appears unannounced on an invoice, not when they are asked.
If they will not agree a price
Do not do it. This feels awkward and it is the correct answer.
Unpriced work is either a gift or a dispute, and you do not get to choose which at the time, the customer does, months later.
Time as well as money
Say whether a variation moves the finish date. Customers who agree to extra work and then complain about the overrun it caused have usually not been told the two are connected.
Unforeseen work
Rot under a floor, foundations needing depth, pipework that must be replaced. Genuine, and reasonably chargeable, but the same rule applies. Photograph it, describe it, price it, get agreement, then do it.
Photographs matter here. "I found rot" is a claim; a photograph is evidence.