On this page
- Start with the paperwork, not the argument
- Question one, did anything you were told or shown fix the price?
- Question two, did you expressly agree to the rise?
- Question three, is this part of the job or an extra bolted onto it?
- Question four, if nothing fixed a price, what counts as reasonable?
- Common price rises that catch people out
- If the deal was done at your kitchen table
- What to say, and in what order
- Frequently asked questions
Start with the paperwork, not the argument
Most people in your position want to have the argument first. Understandable, and it's the wrong order. Documents you already have often settle whether a builder can charge more than the quote. Read them closely before you accept the builder's demand.
This is real money. Our own cost profiles put the average British building job at £32,109 across 828 profiles, so a fifteen per cent walk-up runs to about £4,800.
Four questions help you work out whether you owe it. Did anything fix the price? Did you expressly agree to the rise? Is the charge part of the job or bolted onto it? And if nothing fixed a price, what counts as reasonable?
Six lines to find on your own paperwork before you reply
- The figure, and what the document calls itself. Quote, quotation, estimate or fixed estimate. Write the exact word down.
- The VAT line. Does the number say it includes VAT, and does a VAT registration number appear anywhere on the page?
- The description of the work. Read what that figure covers, then read whatever the document says it leaves out.
- Any line explaining how the price gets worked out. A day rate, a rate per square metre or a provisional sum is a method, not a total.
- Any clause letting the price move, and what it says has to happen before it can.
- The cancellation notice, if you agreed the job at home. They should have given you one on paper or, if you agreed, another durable medium.
Question one, did anything you were told or shown fix the price?
The heading on the document isn't decisive. What matters is whether something told or shown to you fixed a price, and whether you took it into account when you chose this builder. The table sets out five common starting points.
| What you were given | What it is | What it fixes | What can move it |
|---|---|---|---|
| A quote or quotation | A promise to do the described work at an agreed price | The price and scope, including any fair term that already allows the price to move | An agreed variation, an obvious pricing mistake, or an applicable fair adjustment term |
| A fixed estimate | Citizens Advice treats this wording as a quote | The same as a quote | The same rules as a quote |
| An estimate carrying a figure | The trader's best guess at the likely cost | If you relied on it, the estimate and its stated limits become terms under section 50 | The final bill can still differ, but if no price was fixed it must be reasonable under section 51 |
| A day rate, a rate per square metre or a provisional sum | The manner in which the price is to be calculated | The method, not the total | Express agreement to a different method |
| Nothing in writing | An oral agreement may still be binding | Whatever price or method you actually agreed, if you can prove it | If neither the contract nor section 50 fixes a price, section 51 supplies a reasonable price |
When a written figure becomes a term of your contract
Section 50 of the Consumer Rights Act 2015 is one of the provisions that answers you. It puts a term into every contract for a service: "anything that is said or written to the consumer, by or on behalf of the trader, about the trader or the service", where you took it into account when deciding to enter the contract, or when making a later decision about the service.
The statutory question is whether you took the information into account when deciding about the contract or service. A price that influenced your choice can meet that test.
One catch is worth knowing. Anything the builder said or wrote on the same occasion to qualify the figure travels with it, so "subject to what we find under the floor", written on the estimate, is part of the term too. And where the deal was done at your home, subsection (3) pulls the price information they owed you beforehand into the contract as well.
When no price was fixed at all
Section 51 is a narrower fallback than it first appears. It applies only where three things are true at once. You haven't paid a price for the service. The contract doesn't fix one and doesn't say how it's to be fixed. And nothing treated as included under section 50 fixes one either.
That third condition catches people out, but it doesn't turn every written number into a fixed price. Citizens Advice calls an estimate the trader's best guess. If no price or method was fixed, section 51 puts a term into the contract that you pay a reasonable price for the service, "and no more".
Question two, did you expressly agree to the rise?
This is the hinge. Start by checking your phone and messages. Section 50 allows a change to a term where the change "has been expressly agreed between the consumer and the trader", before the contract or later. For price information handed over at your home, subsection (4) is blunter still: a change isn't effective unless expressly agreed.
What express agreement actually looks like
It can be a text saying go ahead at the new figure, a signed variation, or a clear spoken yes to the work and price. Writing is easier to prove, but section 50 doesn't say the agreement itself must be written.
It doesn't look like "we discussed it", or "I did mention it might come to more". Those are conversations about a possible rise, which isn't the same as agreeing one.
So go through your own messages before you reply to anything. If you find a clear agreement to the extra work and price, you owe that agreed amount. It's much better to find that message yourself than to have it read back to you.
Silence is not agreement, and neither is carrying on
Letting a builder keep working after they mentioned the price might go up is not, by itself, express agreement to a new figure. Silence is not agreement. A nod or spoken answer can matter if it clearly accepts the work and price, so read the whole exchange rather than one gesture. The builder will need evidence that you agreed.
Be fair about one thing. A roofer can uncover work that wasn't visible before a tile came up, and some of those charges may be real. Ask what work is needed and what it will cost before they carry on. Get the answer in writing if you can, because that is easier to prove, but a clear spoken agreement can also matter.
Think carefully before paying the disputed sum simply to keep the peace and then asking for it back.
Question three, is this part of the job or an extra bolted onto it?
Two different things get merged here, and they have different answers. One is a change to the price of the work you agreed. The other is an extra charge for something else, added to the invoice at the end. Your contract terms govern the first. Regulation 40 supplies a separate rule for some additional payments.
Extras you never expressly consented to
The Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013 handle this at regulation 40. You owe nothing on top of "the remuneration agreed for the trader's main obligation" unless the trader obtained your express consent before you became bound by the contract. They can't infer that consent from a default option you left alone, such as a pre-ticked box.
If they take the money anyway, the consequence sits in the same regulation. The contract "is to be treated as providing for the trader to reimburse the payment to the consumer". Not a discretion anybody exercises. A term of your contract.
First ask whether the line is an extra service or part of the builder's main job. Regulation 40 deals with additional payments, while the quote and section 50 govern the agreed price for the main work. If you're putting up a new building, hold that thought until we get to kitchen table deals.
Variations you did ask for, and what they should cost
Now the honest half. If you asked for the extra socket, the better tiles or the second coat of paint, you owe a price for it. If no price or method was agreed, section 51 says that price must be reasonable. A builder who prices variations properly before doing them is doing the job right, and that's the builder you want.
Our own profiles put the average kitchen job above thirty thousand pounds, so a mid-job change with kitchen fitters can move real money. Price each change or agree how it will be calculated before work starts.
A fair variation is priced before the work happens, put in writing, and kept separate from the original figure so you can see exactly what moved.
On timing, Beams Renovation's guide says most builders hold quotes open for 30 to 90 days from issue. That's a market convention, not a statutory period in the Consumer Rights Act or the 2013 Regulations. Check what the quote says before accepting it.
Question four, if nothing fixed a price, what counts as reasonable?
If neither your written nor spoken agreement fixed a price or a way to calculate it, this is where you are. Section 51(3) is one sentence long: "What is a reasonable price is a question of fact." No percentage appears anywhere in it.
Citizens Advice sets out what the argument is made of. The estimate you agreed to. Any changes, and why they happened. Anything beyond the builder's control, such as bad weather or the cost of materials going up. It also suggests asking another trader to price the same work, which gives you a useful comparison.
The 10 to 15 per cent rule of thumb, and why we would not lean on it
TradeDoc, a document service written for tradespeople, suggests the original estimate plus 10 to 15 per cent and says that is where most judges land. It gives no source for the figure. The Act says only that reasonableness is a question of fact.
Treating that range as a rule can set an arbitrary ceiling above what the evidence supports. The page is written for tradespeople, not as official consumer guidance.
The stronger argument is the boring one. What the same work costs locally, what you were told during the job about costs changing, and what the builder's own records show about hours and materials.
Common price rises that catch people out
The table below separates several reasons a builder may give. An arithmetic slip is one of them. Citizens Advice says the quoted price still applies unless the mistake was obvious to you. It explains that most people would need to see the mistake.
| What they say | Is it yours to pay | Why |
|---|---|---|
| You asked for extra work | Yes, but not automatically at the invoiced amount | Pay the agreed price or, if none was fixed, a reasonable price under section 51 |
| We found something hidden, explained the extra work and price, and you agreed | Yes, at the agreed price | The agreement to the variation is what proves it |
| We found something hidden and got on with it | Not automatically | Check the original scope and any fair price-adjustment term. Unagreed extra work is not automatically payable |
| Our materials went up | Not on that fact alone | A fixed quote is the starting point. Check whether a fair existing price-adjustment term applies |
| It took longer than we allowed | Not on that fact alone | Extra time doesn't change a fixed quote unless an applicable fair contract term allows it |
| VAT goes on top | Not automatically | Section 230 says mandatory VAT belongs in the total price, but the contract still decides what you owe |
| There was a mistake in the quote | Only if the mistake was obvious to you | Citizens Advice's own test, and the exception most people miss |
| There is an additional payment for something outside the main obligation that you never consented to | No | Regulation 40 treats the contract as providing for that money to come back |
VAT that was never in the number
VAT landing on top of a figure you took to be final is one version of this. Since 6 April 2025, section 230 of the Digital Markets, Competition and Consumers Act 2024 has governed total-price information in invitations to purchase. It says the total price "includes any fees, taxes, charges or other payments that the consumer will necessarily incur". The CMA's price transparency guidance names purchase taxes such as VAT as a mandatory charge, and says presenting a charge separately doesn't make it optional. Where part of the price genuinely can't be worked out in advance, the method has to be given with as much prominence as the headline figure.
A UK business must register in either of two cases. Its taxable turnover for the last 12 months goes over £90,000, or it expects to go over that in the next 30 days. Businesses below the threshold can register voluntarily, so turnover alone doesn't tell you whether a builder is registered. If VAT appears on your invoice, it must carry the trader's VAT number and show VAT separately.
Materials went up after you signed
Citizens Advice is direct: "They can't charge you more if their costs have gone up since they did the quote." That is the starting point for a fixed quote. Check whether the accepted contract already contains a fair price-adjustment term that applies.
An estimate runs differently. Citizens Advice lists the cost of materials going up among the things you weigh in deciding what's reasonable, alongside bad weather and anything else outside the builder's control.
A quote can carry a price-adjustment term. Whether it applies depends on what the term actually says and whether it is fair. A vague line saying "prices subject to change" doesn't by itself explain when or how the price will move.
The job overran
This rise can sound reasonable, but a fixed quote starts from the agreed price. On a fixed quote, extra time alone doesn't change the price. Check whether the contract contains a fair term that applies to the event before accepting an overrun charge.
It gets difficult when the same fortnight was both things at once. The job overran, and somewhere in the middle you authorised extra work. Separate the original fixed scope from the variation. Pay the variation at the agreed price or, if no price or method was fixed, at a reasonable price.
Ask them to split the invoice: original scope on one side, variations priced separately on the other. A builder who keeps proper records can do that.
If the deal was done at your kitchen table
If you made the contract in your own kitchen rather than in a shop or showroom, the off-premises rules may apply. The 2013 Regulations define an off-premises contract to include one "concluded in the simultaneous physical presence of the trader and the consumer, in a place which is not the business premises of the trader". A builder at your kitchen table with a clipboard is the textbook case.
One limit belongs here first, because getting it wrong is worse than never hearing it. These Regulations don't apply to a contract, to the extent that it is "for the construction of new buildings, or the construction of substantially new buildings by the conversion of existing buildings". A new-build contract, and a conversion that creates a substantially new building, sits outside these Regulations to that extent. Their information, cancellation and additional-payment protections don't apply to the excluded construction work. Sections 50 and 51 of the Consumer Rights Act still reach you, because that Act has no construction exclusion. Ordinary repair or improvement work on an existing house isn't caught by that exclusion, but converting one into a substantially new building is.
The paperwork they had to give you
Before you're bound by an off-premises contract, regulation 10 says the trader must give you the information listed in Schedule 2, in a "clear and comprehensible manner", on paper or on another durable medium you agreed to. It has to be legible. That list includes "the total price of the goods, services or digital content inclusive of taxes", or, where the price can't reasonably be calculated in advance, the manner in which it's to be calculated. Where a right to cancel exists, they owe you a cancellation form too.
Regulation 12 adds a second duty. A copy of the signed contract, or a confirmation of it, before performance of the service begins.
If you got none of this, say so in writing. It's a breach in its own right, and it leaves the builder with no paperwork of their own to say the price was something else.
The fourteen days, and the twelve months
Where a right to cancel exists and they never gave you the cancellation information, regulation 31 stretches the deadline. If they hand it over late but inside twelve months, your cancellation period ends fourteen days after you receive it. If they never hand it over at all, the period ends twelve months after the day it would otherwise have ended.
Read that carefully, because it isn't a licence to walk away from work already done. Your request to start early has to be on a durable medium. If you made that request and received the required information, regulation 36 can make you liable for the proportion supplied before you cancelled. If the trader missed those steps, regulation 36(6) says you bear no cost for that work.
The extended period gives you leverage, and it's at its strongest on a job that has barely started.
What to say, and in what order
Order matters more than tone. Establish which document you're holding. Say what you'll pay and why. Pay that part. Put all of it in writing.
We're not your solicitor, and a dispute big enough to threaten the job deserves one. Your paperwork is the best place to start. We build these guides the way we rank tradespeople, and how we assess the providers we list is published in full.
If the money has already left your account, not just been demanded, that's a different problem. Start with getting your money back.
The email that sets out your position
Four things the message has to do, in this order. Name the figure you agreed and say where the agreement appears. Name the extra you're being charged. Ask what express agreement they're relying on for it. Say what you will pay, and by when.
Keep it short and keep the temperature down. You're building a record rather than winning an argument, and if this goes further, that email is likely to be important evidence.
Red flag: four moves to avoid while you build a clear record.
- Paying the disputed amount to keep the peace, then asking for it back
- Agreeing the rise on the phone and putting nothing in writing afterwards
- Holding back the whole balance instead of the disputed part
- Telling them to down tools before you've put the dispute in writing
Pro tip: consider paying the part you don't dispute. In the same message, name the exact sum you're withholding and why. That keeps your written position focused on the disputed charge. Get legal advice before withholding the full balance in a high-value dispute.
If the relationship is past saving, get fresh prices from other builders in your area and check the builder before you accept the next quote. Do those checks before you commit.
Frequently asked questions
Is a builder's quote legally binding in the UK?
Generally, yes, once you accept it. Citizens Advice describes a quote as a promise to do work at an agreed price. Check the described scope and any fair term that already allows the price to move. A later variation must be agreed, and an obvious pricing mistake can also affect the result.
How long is a builder's quote valid for?
No statute sets a standard period. Beams Renovation's guide says most builders hold quotes open for 30 to 90 days, with 30 days common where materials carry most of the price. Check the expiry date before you accept. If there isn't one, ask how long the builder will hold the price and get the answer in writing.
Does a builder's quote have to include VAT?
If VAT is payable, it belongs inside the total rather than on top of it. Section 230 of the Digital Markets, Competition and Consumers Act 2024 counts any tax you'll necessarily incur as part of the total price. The CMA names VAT as a mandatory charge. A VAT invoice must show the trader's VAT number and display VAT separately.
Do I have to pay a builder who is asking for more money after we signed?
Signing doesn't make every price rise payable. Start with what the contract fixed and any term that allowed the price to move. You then owe an agreed variation, or a reasonable price where no amount or method was fixed. Section 50 means information you relied on and its qualifications can become contract terms, while silence alone is not agreement.
Can I refuse to pay a builder?
You can dispute the part above the amount you say is due. Tell the builder in writing which sum you're paying, which you're withholding and why. Citizens Advice recommends paying the quoted amount and putting your position in writing. Get legal advice before withholding the full balance in a high-value dispute.
What is the difference between a quote and an estimate in the UK?
A quote is a promise to do the work at an agreed price. An estimate is the builder's best guess and can change. If you relied on the estimate, section 50 can make it and its qualifications contract terms. If no price was fixed, section 51 says the final bill must still be reasonable.
Can I cancel after a builder quoted me in my own home?
Usually, if you made the contract at home. A service contract normally has a 14-day cancellation period. The right doesn't cover the urgent repair itself when you specifically requested the visit, though extra services can still be covered. A new-build contract is also outside these Regulations. The trader must give you the cancellation form on paper or another durable medium you agreed to. Missing cancellation information can extend the deadline by up to 12 months. Early work is chargeable only if regulation 36's request and information conditions are met. The right can also end after full performance if you gave the required consent and acknowledgement.