Can a builder charge more than a quote? Your rights under UK law
The short answer: in England and Wales, no — a builder cannot lawfully charge more than a fixed quotation for the agreed scope of work unless you expressly agreed to a variation in price and scope beforehand. Under Section 50 of the Consumer Rights Act 2015, any spoken or written statement about price taken into account by the consumer is binding. If you only received an "estimate", the builder can only charge a "reasonable price" under Section 51, which courts typically cap at 10%–15% above the estimate unless exceptional unforeseen work was agreed.
REVIEWED BY: Sean McNamara on 2026-09-03
The crucial distinction: Quote vs Estimate
Before paying or disputing an unexpected invoice, check the exact wording on your initial paperwork:
| Feature | Formal Quotation (Quote) | Ballpark Estimate | Day-Rate / Cost-Plus |
|---|---|---|---|
| Legal Status | Legally binding contractual offer | Non-binding educated guess | Variable fee based on hours/materials |
| Can it change? | No (unless written variations agreed) | Yes, but strictly limited to a reasonable sum | Yes, tracks actual hours and receipts |
| Statutory Provision | Consumer Rights Act 2015 s.50 | Consumer Rights Act 2015 s.51 | CRA 2015 s.51 (Reasonable price) |
| Court Standard | Fixed price enforceable as agreed | 10%–15% tolerance benchmark | Burden on trader to prove hours/costs |
| Who bears risk? | The builder absorbs miscalculations | Shared risk for genuine surprises | The homeowner carries the cost risk |
When a builder is legally allowed to charge extra
There are only three legal circumstances under which a builder can demand more than the original quoted sum:
1. You agreed to a variation in scope (in writing): If you requested extra plug sockets, upgraded bathroom tiles, or decided to move a structural wall, the builder is entitled to be paid for that extra work. However, the price or rate should be agreed before the work is carried out. 2. The quote contained explicit exclusion clauses or provisional sums: If the quote clearly stated "Excludes groundworks remediation if underground obstructions are found" or included a "Provisional Sum" of £1,500 for kitchen units, the final cost will reflect the actual supply cost. 3. Genuine unforeseen structural emergencies: If opening up a ceiling reveals immediate danger of collapse that required urgent stabilization to prevent injury or catastrophic damage, reasonable mitigation costs may be chargeable.
When extra charges are completely unlawful
A builder cannot charge you extra for:
- "It took longer than we thought": Under a fixed quote, miscalculating labour time is entirely the builder's commercial risk. They cannot charge you for their own slow progress.
- "Building materials went up in price": Unless the contract had an express "materials price fluctuation clause", a quote binds the contractor to the agreed price for the validity period.
- Work that was inherently necessary to complete the job: If a builder quoted for fitting a roof, they cannot bill extra for ridge tiles and battening claiming they "didn't realize they'd be needed". Work necessary to deliver the quoted job is deemed included.
- Unagreed verbal extras: If the builder carried out work without asking you first, you are not obliged to pay for it. Under Section 50 of the Consumer Rights Act 2015, they cannot unilaterally increase the contract price.
What about an "Estimate"? The Section 51 rule
Many builders intentionally write "Estimate" at the top of their paperwork to give themselves wiggle room. However, an estimate is not a blank cheque:
- Section 51 of the Consumer Rights Act 2015 states that where a contract does not fix a price, the consumer must only pay a "reasonable price", and no more.
- In UK case law (Croshaw v Pritchard and Renwick [1899]), courts established that a professional estimate provides a baseline expectation. A builder cannot exceed an estimate by more than 10% to 15% unless they can demonstrate that site conditions changed fundamentally and that they notified the homeowner immediately when the overrun became apparent.
- If a builder estimated £20,000 and presents a final invoice for £28,000 (+40%) without prior written warning, the excess £8,000 is legally disputable under Section 51.
Step-by-step: what to do if your builder demands more money
1. Do not panic-pay
Never pay disputed extra sums out of fear that the builder will walk off. Paying without written qualification weakens your legal position, as the builder will argue you affirmed the variation.
2. Request a fully itemised breakdown
Send a written request (email or text) immediately:
"Thank you for your invoice dated [date]. The total exceeds the agreed fixed quotation dated [quote date] of £[amount] by £[excess amount]. Please provide an itemised breakdown showing each variation claimed, when it was agreed, and the supporting labour and materials receipts."
3. Check for written variation orders
Review all your WhatsApp messages, emails, and notes. If a variation was never approved in writing by you, you are entitled to stand on the original contract sum.
4. Send a formal dispute notice
If the builder insists on the inflated sum or threatens to down tools, send a formal written response:
"The agreed quote of £[amount] is legally binding under Section 50 of the Consumer Rights Act 2015. I am willing to pay the contracted sum upon completion of the works. I dispute the additional £[amount] as it was never agreed. Please confirm by [date in 7 days] that work will proceed in accordance with our contracted schedule."
5. Use the Quote & Overrun Calculator
To calculate the exact allowable vs disputed sum and determine your net legal exposure, use our free Quote vs Estimate Dispute Calculator.
If the builder down tools or walks off
If the builder refuses to work until you pay an unagreed overrun, they are committing an anticipatory repudiatory breach of contract.
Do not immediately hire someone else without following formal procedure, or you could face a counterclaim. Follow our comprehensive guide: Builder walked off the job — what to do next.
Related guides & tools
- Quote vs Estimate Dispute Calculator — check your exact statutory rights
- Builder walked off the job — what to do — notice to complete procedure
- Letter before action builder template — formal 14-day pre-action notice
- Consumer Rights Act 2015 building work — sections 49–56 explained
- How to take a builder to small claims court — step-by-step court procedure
This page provides general consumer legal information in England & Wales and does not constitute formal legal advice. Sourced from the Consumer Rights Act 2015 and civil case law. Verified 2026-09-03.
Turning your evidence into a court-ready bundle? EvidenceCanvas (Casewright) helps you organise your evidence and draft pre-action documents for the small claims track. It is not a law firm and does not give legal advice.
Reviewed by Sean McNamara · 2026-09-03 · Independent information directory — not legal advice.