If the work changes after a quote is accepted, describe the change, price its effect and get clear approval before carrying it out. Record any extra time as well as the money. A remembered conversation is a poor substitute when the final invoice arrives.

Start with the accepted scope. An awkward task, a pricing mistake or a repair to your own work is not automatically a customer-funded extra.

Check what was already agreed

Read the quote, drawings, specification and relevant messages. Establish whether the proposed work changes the agreement or is needed to deliver what you already promised.

For a consumer contract, important information about the service can form part of the agreement. Do not rely on a clause giving you unrestricted power to increase the price. The CMA’s fair-contract guidance explains why broad variation terms can be unfair.

If you are working for a main contractor, check its variation procedure too. Identify who can approve additional work and whether a formal instruction is required. The person on site may not have authority to agree the extra charge.

Describe the change before pricing it

Write down what is being added, removed or altered. Explain why it is outside the original scope, using a photograph where that helps.

• A different fitting or material specification.

• Another room, circuit or appliance added to the job.

• A revised layout after work has started.

• A concealed problem that could not reasonably be assessed earlier.

• Changed access or sequencing that affects the agreed work.

For hidden problems, distinguish the new discovery from a blanket claim that every unexpected cost belongs to the customer. The contract and circumstances still matter.

Show the price and timing together

Calculate additional labour, materials, equipment and disposal costs. Include a credit where work is removed. State the total change the customer will pay, including VAT where applicable.

For consumer prices, unavoidable charges should be included in the displayed total. Where you cannot calculate a total yet, explain the method and agree a sensible limit before going further. See the CMA’s price transparency guidance.

Explain whether the change affects the finish date, another trade or the next payment stage. Agreement to a price is not useful if the customer has not understood that it also changes the programme.

Get approval that refers to the change

Give the change a reference and ask for a clear written acceptance. Keep the agreed version with the original quote. Do not proceed on a vague “should be fine” if the price or work is still uncertain.

Template: variation record

Variation [reference] to quote [number]: [describe changed work]. Reason: [why it is outside the agreed scope]. Price change: £[increase or credit], including [VAT treatment]. Revised total: £[amount]. Timing change: [effect]. Payment due: [agreed stage or date]. Please confirm acceptance of this change before the work proceeds.

This is an example of the information to record, not a legal form suitable for every contract. Replace the placeholders and attach any drawing, photo or specification the customer needs to understand it.

Handle urgent discoveries carefully

If you uncover something unsafe, make the immediate situation safe within your competence and explain what you found. Record why action was necessary and seek approval as clearly as the circumstances allow.

Do not use urgency to avoid discussing costs. If the next step can wait safely, give the customer the options before committing them. Ask for specialist or legal advice where there is a dispute about responsibility, access or the right to continue.

Keep the invoice consistent with the approval

List approved changes separately and refer to their references. Show credits as clearly as additional charges. Deduct earlier payments correctly and make the final balance easy to check.

If several changes happen during the job, maintain a running total. Send the current position after each accepted variation rather than leaving the customer to add several messages together.

TradePilot keeps customer, quote, job, photos and invoice records connected. It does not decide whether extra work is legally chargeable or obtain approval on your behalf. A clear original scope helps; use the trade quote checklist before the next job.

Written by Chris, founder of TradePilot. General information, not legal advice. Last reviewed 16 September 2026 against the official sources linked above.