HOW TO HIRE · PLUMBING & HEATING

How to hire a boiler replacement engineer in the UK
The checks, the questions and the paperwork.

A boiler replacement is gas work for a Gas Safe engineer only, and it must be notified. How to check them, compare quotes and get the certificate.

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THE 60-SECOND VERSION

Hiring a boiler replacement engineer in five steps

  1. Check the licence firstEvery engineer quoting should give a Gas Safe licence number; check it by text to 85080 before comparing prices.
  2. Decide like for like or a changeSame type in the same place is the simple job. A move or a system change is a different quote.
  3. Get the scope in writingBoiler model, flue, filter, system clean, controls and removal of the old boiler, all listed.
  4. Ask about the old systemSludge, tanks and microbore pipes change the job. A good engineer looks at them.
  5. Chase the certificateThe compliance certificate should follow the notification; gov.uk says within 8 weeks.

BEFORE YOU BOOK

Check before you book

Gas Safe Register

The 1998 Gas Safety (Installation and Use) Regulations, and the Northern Ireland Regulations of 2004, make Gas Safe registration a legal condition of being paid to remove or fit a gas boiler. A friend 'who knows boilers' is breaking the law if they are not registered.

Text 'Gas' and the licence number to 85080, or ring 0800 408 5500. gassaferegister.co.uk →

The categories on the card

HSE explains that the back of the Gas Safe ID card lists the work the engineer is qualified to do. A boiler replacement needs the boiler category, not just cookers or fires.

Ask to see both sides of the card when the engineer visits to survey. hse.gov.uk →

Notification and the compliance certificate

A replacement boiler counts as notifiable building work in England. The Gas Safe engineer self-certifies and notifies it, and the compliance certificate comes afterwards — gov.uk says within 8 weeks.

Write the expected certificate into the quote, and chase it if it has not arrived. gov.uk →

A heat pump comparison and the Boiler Upgrade Scheme

A gas boiler gets no grant, but the Boiler Upgrade Scheme in England and Wales pays towards a heat pump through an MCS certified installer. If your home might suit one, a second quote costs nothing.

Read the gov.uk eligibility rules before you commit to another gas boiler. gov.uk →

VAT

Replacing a gas boiler is standard-rated at 20%; 5% applies only to the part a grant pays for when the household includes a qualifying person, aged 60 or over or on certain benefits, in their main home. Over the £90,000 registration threshold a trader must charge it and show it separately; under it there is no VAT and no VAT number.

Ask the engineer to show the boiler VAT apart from any zero-rated controls, and for the VAT number on the quote. gov.uk →

“Is the boiler replacement like for like, and in the same place?”

A good answer: A clear yes or a clear 'no, and here is why it costs more'. A new position means new pipes, a new flue and more time.

“Will you flush the system before the new boiler goes in?”

A good answer: Yes, a chemical clean or a power flush depending on the state of the water, and a filter on the return.

“Does the new boiler need a bigger gas pipe?”

A good answer: They check the gas supply size from the meter. An undersized pipe is a common reason a replacement runs over.

“Who disposes of the old boiler and any tanks?”

A good answer: Included in the replacement price, or priced as a separate line.

“How will the boiler replacement be notified, and when will the certificate come?”

A good answer: They notify it, and the compliance certificate follows; gov.uk says within 8 weeks.

“What is the warranty on the new boiler, and what does it need?”

A good answer: The maker's warranty length, registration, and the yearly service it depends on.

“What controls are you fitting with the new boiler?”

A good answer: Named controls — thermostat, programmer or a smart thermostat — and whether any are zero-rated for VAT.

Getting the quote right

  • The new boiler named by make, model and output
  • Flue, condensate pipe, filter and system clean shown as separate items
  • Removal and disposal of the old boiler and any loft tanks
  • Who notifies the replacement and when the compliance certificate is expected
  • Who actually attends on fitting day — the Gas Safe engineer on the quote, employed or subcontracted
  • The VAT number, and VAT at 20% on the replacement shown on its own

Walk away if

  • Cannot give a Gas Safe licence number that matches their name
  • Quotes without looking at the old boiler, the flue or the gas pipe
  • Offers a cheaper price 'without the paperwork'
  • Wants most of the money before the boiler arrives
  • Says the old system will not need a clean, whatever its condition
LOW
£1,500
TYPICAL
£2,100
HIGH
£3,500

What a boiler replacement engineer costs: £1,500–£3,500 per install

A boiler replacement is quoted as a fixed price after a survey; the boiler, the flue and the state of the old system decide it. Boiler Replacement price guide →

Guide prices compiled by the Locufy team from published Irish and UK provider price lists and 2026/27 cost guides. Updated 2026.

KNOW WHAT TO LOOK FOR? NOW FIND ONE

Boiler replacement engineers near you, with the badges that matter shown

ID checked, trader status and one score from every review — on the card, before you message anyone. Nearest first. No account needed to look.

Or post the job free and let them come to you.

  1. Isolate and drainGas, power and water are isolated and the system drained before the old boiler comes off the wall.
  2. Remove the old boilerThe old boiler and any redundant tanks or pipework are taken out and capped safely.
  3. Clean and fitThe system is cleaned, then the new boiler, flue, filter and controls are fitted.
  4. Test and commissionGas tightness, flue checks and combustion readings are taken and written on the commissioning checklist.
  5. Notify and hand overThe replacement is notified, the controls explained, and the papers left with you.

Like-for-like replacement
The same type of boiler in the same position, using the existing flue route where safe.
Gas tightness test
A pressure test that proves the gas pipework does not leak.
Power flush
Pumping cleaning chemicals through the radiators at high flow to shift sludge.
Inhibitor
A chemical added to heating water to slow corrosion.
Output (kW)
How much heat or hot water the boiler can deliver; it must match the home.
Building Regulations compliance certificate
The certificate that follows notification of a new or replacement boiler.

AFTER

When the job is done

File the compliance certificateKeep it with the house papers; it is the proof the replacement was notified and certified.
Look at the commissioning recordThe readings taken when the boiler was first run should be written in the boiler's checklist.
Check heating and hot waterEvery radiator warm, hot water at the taps, the pressure gauge in the normal band and no fault code.
Review the visitA few lines on the boiler replacement help the next household choose. If there is a problem, the make-it-right step sends it to the boiler replacement engineer before your review appears.

STEP 1Complain to the boiler replacement engineer firstStart with an email to the boiler replacement engineer: the problem, photos and what would put it right. A trader's boiler replacement is covered by section 49 of the Consumer Rights Act 2015, and the remedies — doing it again, or a price reduction — follow from sections 55 and 56.
STEP 2Use the make-it-right stepA score under four stars opens the make-it-right step: you choose whether the boiler replacement engineer gets the chance to put the boiler replacement right first, and we chase it to an end before you publish.
STEP 3Unsafe or unregistered gas workReport it to Gas Safe Register; HSE enforces the gas safety regulations and works with the register's investigators.
STEP 4Small claims, if money is owedA claim against the boiler replacement engineer that will not settle can go to court without a lawyer — the small claims track for up to £10,000 in England and Wales, simple procedure for up to £5,000 in Scotland, and the small claims court for up to £5,000 in Northern Ireland.

Hiring a boiler replacement engineer: questions people ask

Yes. Removing and fitting a gas boiler for pay is restricted by law to engineers on the Gas Safe Register, in England, Wales, Scotland and Northern Ireland.

A Building Regulations compliance certificate, once the engineer has notified the work; gov.uk says it should arrive within 8 weeks. Keep the commissioning record and warranty papers too.

Not for another gas boiler. The Boiler Upgrade Scheme in England and Wales pays towards heat pumps, and Scotland has the Home Energy Scotland grant and loan.

£1,500–£3,500 per install, with about £2,100 typical for a like-for-like swap. What pushes it up or down is in the boiler replacement price guide; search above by town for engineers in your area.

Most like-for-like replacements take a day; extra pipework or a new flue route adds a second day.

Yes, at 20%. HMRC's Notice 708/6 keeps gas boilers at the standard rate; only qualifying heating controls are zero-rated until 31 March 2027.

MORE GUIDES

More hiring guides in plumbing & heating

How to hire: Boiler InstallationHow to hire: Boiler Service & RepairHow to hire: Power FlushingHow to hire: Central Heating InstallationHow to hire: Heat Pump InstallationHow to hire: Gas EngineerHow to hire: Radiator InstallationHow to hire: Emergency PlumberAll 701 hiring guides →

Boiler replacement engineers near you

Boiler replacement engineers in LondonBoiler replacement engineers in ManchesterBoiler replacement engineers in BirminghamBoiler replacement engineers in GlasgowBoiler replacement engineers in BelfastAll boiler replacement engineers on Locufy →

Sources — checked October 2026

  1. Gas Safety (Installation and Use) Regulations 1998, regulation 3
  2. Gas Safety (Installation and Use) Regulations (Northern Ireland) 2004, regulation 3
  3. HSE — Gas Safe Register: the scheme, its coverage and the ID card
  4. Gas Safe Register
  5. gov.uk — building regulations: use a competent person scheme
  6. gov.uk — VAT on energy-saving materials and heating equipment (Notice 708/6)
  7. gov.uk — apply for the Boiler Upgrade Scheme
  8. Consumer Rights Act 2015, section 49 — reasonable care and skill
  9. mygov.scot — make a court claim for money
  10. Energy-saving materials and heating equipment (VAT Notice 708/6) — 3.3 Central heating systems (5% only when grant-funded); 2.23 otherwise standard-rated
  11. GOV.UK — VAT rates
  12. GOV.UK — Register for VAT: when to register