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
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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