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Citizens Advice tells homeowners that a trader can't charge more than the quoted price unless the customer asks for extra work, the trader tells them extra work is needed and they agree to pay for it, or the trader made a mistake writing down or working out the price. Extra work you do first and mention later is work you may not get paid for. A variation form template gives you one page to record each change before you start it: what changed and why, the price, the effect on time, and who agreed it and how.
Below is a variation form to print or copy, how to word and price a change, who has to approve it, a filled-in bathroom example and a simple log that makes the final invoice add up. For how variations fit with the rest of the job record, see the guide to recording trade jobs on site.
The variation form for each change
Use one form for each change, numbered against the quote: V1, V2 and so on. The same form covers extra work, a swapped item and work the customer has dropped, so a credit is recorded the same way as a charge. Keep a pad in the van, or copy the layout into your job app or a shared spreadsheet.
Fill it in before the extra work starts, not when you pack up. The rest of this guide covers the parts that cause arguments: deciding what counts as a variation, the wording, the price, who can say yes, and what to do when the answer is no.
When a change counts as a variation
A variation is any change to the work, the price or the finish date after the customer has accepted the quote. That includes work the customer asks for, work you find is needed, items they swap, and work they decide to drop. If it changes what the customer pays or when the job finishes, write it up.
Some changes aren't variations, because the quote already deals with them. Using a provisional sum or a prime cost (PC) sum is settled against the allowance in the quote, so you record what was used rather than raising a new price. Putting right your own mistake isn't a variation either: it costs the customer nothing, though a note on the job sheet still helps.
Rising material prices are not a reason to change a quoted price part-way through. Citizens Advice also says a trader can't charge more because their costs have gone up since the quote. If your prices are moving, put a short validity date on the quote instead.
| Situation | Is it a variation? | What to do |
|---|---|---|
| Customer asks for an extra socket or radiator | Yes | Price it and get approval before you start |
| You find rotten boards under the old bath | Yes, if it costs more or takes longer | Stop, photograph, price, get approval |
| Customer drops part of the work | Yes, as a credit | Agree the credit in writing, as for a charge |
| Customer picks tiles within the PC sum | No | Record the choice and cost against the allowance |
| You put right your own mistake | No | No charge; note it on the job sheet |
| Your material costs go up mid-job | No | Hold the quoted price; shorten validity next time |
Word the change for a text message
Most customers approve variations on their phone, often while you're still on site and they're at work. So write the change so it makes sense on its own, with nothing to look up.
Say what was found or asked for, what you'll do about it, and what it costs including VAT. Then say what it does to the finish date, and how to approve. "Variation 1 to quote Q-0623: replace the rotten bottom 300mm of the back door frame and refit the door, £145 plus VAT (£174 including VAT), adds two hours. Photos attached. Reply YES to approve" works. "Found some rot in the frame, need to sort it, about another hundred or so" doesn't, because the customer has nothing to agree to.
Attach a photo whenever the change comes from something you found. A customer at work can't see the bottom of their door frame, and a clear photo of the rot answers most questions before they're asked. Photograph it before you start, so the photo also shows why the work was needed if the invoice is queried later.
Number every variation against the quote and its version: "Variation 2 to quote Q-0623 version 1". The number is what ties the text, the form, the job sheet and the invoice together. Under section 50 of the Consumer Rights Act 2015, what you say or write to the customer about the work can become part of the contract, subject to any change you've both expressly agreed. A numbered variation, agreed in writing, is that agreed change.
Price the variation before you do the work
A variation price agreed afterwards is a negotiation you've already lost, because the work is done and the customer knows it. Price it before you start, even if that means stopping for ten minutes to work it out.
Pricing is quicker when the quote already sets out how changes are priced, as the guide to writing a trade quote suggests: your day or hourly rate, your markup on materials, and how VAT is added. Then a variation is arithmetic the customer has already seen, not a new figure from nowhere.
Show the price the way the quote did: labour, materials, a subtotal, VAT and the total including VAT. A homeowner who agreed to "£220" and sees £264 on the invoice will feel caught out, even if "plus VAT" was in the text. Put the including-VAT figure in the message every time.
If you can't price it accurately until you open something up, agree a ceiling instead: "up to £300 plus VAT, charged at the actual time and materials, and we'll stop and ask before going over". A ceiling still gives the customer a figure to approve. An open-ended "whatever it takes" doesn't.
Credits work the same way. If the customer decides to paint the ceiling themselves, agree what comes off the price, write it on a form as a credit, and show it on the invoice. A credit that's agreed but never written down is easy to forget, and the customer won't forget it.
Get the approval from the person who pays
The person letting you in isn't always the person who pays. A tenant can't approve extra cost on a landlord's property, and a letting agent may only be able to approve up to a set amount before asking the landlord. Find out who approves extra cost before the job starts, and write their name on the quote and at the top of every variation form.
Get the approval in a form you can keep: a signature on the form, a text reply, or an email. A text that names the variation number and price, with a "YES" reply, is enough for most domestic work. A conversation on the doorstep isn't, because a month later neither of you can prove what was agreed or at what price. If the customer agrees in person, ask them to sign the form there and then.
Business Companion, the trading standards guidance for businesses, says consumers should be asked to expressly consent to additional charges, and that they won't be liable for extra payments they haven't actively agreed to. So don't assume a yes: the customer has to agree to the extra charge themselves, and the form or message should show that they did.
For business customers, landlords and agents, ask whether a variation needs a new or amended purchase order. A variation approved by the site contact but missing from the order can sit unpaid for weeks while their accounts team asks questions.
Record the approval on the form: who, how and when. "Approved by Ms Okafor by text, 9.20am, 3 March" takes ten seconds and settles most later disputes.
When the customer says no or doesn't reply
A no is an answer you can work with. Record it on the form as declined, with what you advised and the date, and carry on with the work you were contracted to do. If what you found means part of the quoted work can't be finished as described, explain that in writing too, and agree how to finish the job.
If the customer can't be reached, don't do the extra work and hope. Stop at the quoted scope, leave the work tidy and safe, and record that you're waiting for a decision. Text them the variation so it's waiting when they look at their phone. Doing the work "to save a trip" is how traders end up arguing over an invoice they can't support.
If the customer wants time to think, put a date on it: "Customer to decide by Friday". That keeps the decision visible on the form and the job sheet, rather than relying on someone remembering to ring.
A declined variation is still worth keeping. If the customer later reports a problem with the part you recommended fixing, the form shows you spotted it, explained it and were told not to go ahead.
Example: three variations on a bathroom job
This is an invented example to show the form and the log in use. The names and prices are made up and are not a guide to what bathroom work costs.
Illustrative example: variations on a bathroom refit
Business: Brookside Plumbing (VAT registered); quote Q-0517, version 1, accepted for £5,400 plus VAT (£6,480 including VAT)
Customer: Ms Okafor, homeowner, approves all costs herself, reachable by text during the day
V1, found on site: rotten floorboards under the old bath; replace about 1.2 square metres with 18mm ply; £220 plus VAT (£264 including VAT); adds half a day; photos sent; approved by text, 9.20am, 3 March
V2, customer request: heated towel rail instead of the quoted radiator; extra cost of the rail £90 plus VAT (£108 including VAT); no change to finish date; approved by signature on the form, 4 March
V3, work left out: customer will paint the ceiling herself; credit £120 plus VAT (£144 including VAT); approved by text, 4 March
Net change: £190 plus VAT (£228 including VAT)
New job total: £5,590 plus VAT (£6,708 including VAT)
The plumber finds the rotten boards when the bath comes out on the first morning. They photograph the boards, fill in a variation form, and text it to Ms Okafor, who is at work. She replies YES within the hour, and the boards go in that afternoon. The next day she asks about a heated towel rail, and signs V2 on site. She also decides to paint the ceiling herself, so the plumber writes V3 as a credit rather than just leaving the painting out.
The invoice shows the quote, then each variation by number, then the new total. Ms Okafor can see where every pound of the extra £228 came from, and she has already agreed to each line. Our invoice template for trade work has a layout with space for each variation line.
Keep a variation log for the invoice
On a job with more than one change, a short log stops variations going missing between site and office. Keep one log per job, on the back of the job sheet or as a tab in the job's spreadsheet, and add each variation as it's agreed.
| No. | Change | Price incl. VAT | Approved by and how | Status |
|---|---|---|---|---|
| V1 | Replace rotten boards under bath | +£264 | Ms Okafor, text, 3 March | Done |
| V2 | Heated towel rail instead of radiator | +£108 | Ms Okafor, signed form, 4 March | Done |
| V3 | Ceiling painting left out | −£144 | Ms Okafor, text, 4 March | Credited |
The office invoices from the quote plus the log, not from memory. Each line on the invoice carries the variation number, so a customer who queries a figure can be pointed straight to the form they approved. Declined variations stay on the log marked "declined", so the record shows what was offered.
On a longer job with stage payments, add the approved variations to the next stage invoice rather than saving them all for the end. The customer pays for each change soon after agreeing it, while the reason is fresh, and the final invoice holds fewer surprises for either of you.
The same numbering works in a job app. Many job apps let you add a variation or extra to a job with its own price and approval note, and some let the customer approve from a link. Whatever you use, check that the approval and its time are stored with the job and come through to the invoice, not left in a text thread on one engineer's phone.
Once the job is finished, keep the variation forms with the quote, the job sheet and the invoice. If the customer queries the bill months later, the four together show what was quoted, what changed, who agreed and what was charged.
Separate jobs and the right to cancel
Most variations change a job the customer has already agreed to. Some extras are closer to a new job, and the rules on contracts agreed in the customer's home can apply to them.
Business Companion's guidance on off-premises contracts gives the example of a plumber called out to replace a broken immersion heater who, while there, offers to repair a dripping tap. An urgent repair the customer asked for can be exempt from the right to cancel, but Business Companion says that exemption doesn't cover other goods or services provided at the same time. So the dripping tap repair, if done during the visit, keeps a cancellation right.
When an extra is in fact a separate job, such as a second room or a different trade's work, treat it as a new quote. If it's agreed in the customer's home, the cancellation information and cancellation form apply to it, as to any job agreed there, unless an exemption applies; Business Companion lists them, including contracts for £42 or less. Our quote template for trade work sets out what to give and how to record a request to start early.
Business Companion's guidance covers England, Scotland and Wales; Northern Ireland has separate guidance. This is not legal advice. It summarises the guidance and legislation linked here. If you're unsure whether a change is a variation or a new contract, take advice before you rely on it.
The guide to invoicing and payment terms for trade work covers putting the agreed variations onto the final invoice and chasing payment if it's late.
Use the form on your next extra
Print a few variation forms and put them in the van, or add the layout to your job app today. The next time a customer asks "while you're here, could you…", or you find something behind a panel, fill in the form before you pick up a tool: what changed, the price including VAT, the effect on time, and the customer's yes.
Check your job app, then record the variation on site
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Job sheet template: eight fields for every trade visit, with a filled-in example
The eight fields that let the office invoice without ringing site, with a line for each agreed variation.
Sources checked for this guide
Extra charges, changes to agreed work and cancellation points checked against Citizens Advice, legislation.gov.uk and Business Companion guidance. These are the primary sources used in this guide.