How to Read a Builder's Quote in 2026 UK — the 7-Step Checklist
A UK builder's quote in 2026 is only as good as the spec it references. Compare on a like-for-like basis by checking these seven things: scope, prime-cost (PC) sums, provisional sums, VAT treatment, payment terms, retention and exclusions. Miss any one and you're not comparing apples to apples — you're comparing apples to a price tag attached to nothing. Here's how to spot the difference between a real quote and a guess.
What does a good UK builder's quote look like in 2026?
A complete 2026 UK builder's quote has all of these:
- Itemised scope of works (not just a single "all works" line)
- A clear distinction between quote (fixed price) and estimate (best guess)
- Specific Prime Cost (PC) sums for items you choose later — kitchen, bathroom suite, ironmongery
- Provisional sums (with a stated allowance) for items not yet specified — e.g. drainage diversions
- VAT treatment stated in writing — standard 20%, reduced 5%, or zero for new-build
- Stage-payment schedule tied to milestones, not weeks
- Retention (typically 2.5–5%) released on practical completion and again 12 months later
- Exclusions clearly listed — e.g. "asbestos handling not included"
Red flags: single-line lump-sum prices, no VAT line, no payment schedule, deposit demand over 10%, no insurance details, no contract reference (JCT MW or similar). If any one of these is missing, ask for a revised quote before signing.
The 7-step checklist before you sign
Step 1 — Check it's actually a quote, not an estimate
In UK contract law, a quote is a fixed-price offer that becomes legally binding when you accept it. An estimate is a best guess and can change. Many builders use the terms loosely — if the document says "estimate" anywhere on it, the price is not binding and the builder can re-price during the works. Ask explicitly: "Is this a fixed-price quote?" Get the answer in writing. The legal distinction has been confirmed repeatedly by UK county courts and HMRC's contract guidance.
Step 2 — Verify the scope of works line by line
A good 2026 UK quote lists the scope item-by-item with a quantity. Bad quotes lump everything under "build extension as discussed" — which means the builder can later argue any item wasn't part of the scope. Each measurable item should appear: m² of brickwork, m² of plasterboard, linear metres of skirting, number of sockets, number of downlights. Ask for a written specification document if the quote itself is short — the spec is what the price actually references.
Step 3 — Identify Prime Cost (PC) sums
A PC sum is a budget allowance for items the homeowner will choose later — kitchen units (£6,000–£18,000 typical PC), bathroom suite (£1,500–£5,000), ironmongery (£300–£800), tiles (£25–£60/m²). The PC sum is replaced by the actual cost on invoice plus a typical 10–15% builder mark-up. Make sure every PC sum is realistic for what you actually want — a kitchen PC of £4,000 is fine for an IKEA Metod kitchen but won't cover a mid-range Howdens spec, and the builder will then issue a variation increasing the bill.
Step 4 — Identify provisional sums and ask what they cover
A provisional sum covers work that's known to be needed but can't be priced exactly yet — typically drainage diversions, asbestos survey/removal, structural steel sizing once the SE has signed off. PC sums let YOU choose; provisional sums let the BUILDER discover the actual cost. Provisional sums in a 2026 UK extension typically run £2,000–£6,000 in total. If a quote has more than 10% of the total as provisional sums, the builder hasn't priced the job — they're guessing. Push back and ask for a fixed price on as many items as possible.
Step 5 — Check VAT treatment
UK building work VAT in 2026: standard 20% on extensions, alterations and most refurbishments. Reduced 5% on renovations of properties that have been empty for 2+ years and on energy-saving materials installed under the 2022 zero-rate extension. Zero-rated on new-build dwellings (the builder doesn't charge VAT but reclaims their input VAT). The quote MUST state "plus VAT" or "inclusive of VAT". A 2026 UK quote that's silent on VAT is non-compliant under the Consumer Contracts Regulations — ask in writing and store the answer.
Step 6 — Stage payments and retention
A safe 2026 UK stage-payment schedule for a £80,000 single-storey extension: 10% deposit on contract signing, 25% on first lift to DPC, 25% on first-fix complete (roof watertight), 25% on second-fix complete, 10% practical completion, 5% retention released after 12-month defects period. Refuse front-loaded schedules — a builder asking for 30% on day 1 is funding their cashflow with your money. Always link payments to milestones, never to calendar dates.
Step 7 — Insurance, warranty and contract
Verify three pieces of paper before signing: (1) £2m+ public liability insurance certificate in date — ring the insurer to confirm the policy is live; (2) 10-year structural warranty via FMB Build Assure, LABC Warranty or similar on extensions and structural work; (3) a written JCT Homeowner Contract (or JCT Minor Works). Builders refusing JCT in 2026 — walk away. Sole-trader builders without insurance — walk away. Without all three, you have no real protection if the works stop midway through.
The five red flags that should make you walk away
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Common Questions
How we sourced these rules
- JCT — Joint Contracts Tribunal — UK construction contract authority
- HMRC — VAT for builders — UK construction VAT rates and exemptions 2026
- FMB — Federation of Master Builders — contract guidance and Build Assure warranty
- RICS — Royal Institution of Chartered Surveyors — PC and provisional sum definitions
Last fact-checked: . Always have a major contract reviewed by a construction-savvy solicitor or RICS surveyor before signing if the contract value exceeds £50,000.
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