Gas engineer invoice template UK (2026): boilers, heat pumps, CIS and VAT

A gas engineer invoice in the UK is not one document. A homeowner boiler service, a landlord CP12, a contractor new-build heating package and a residential heat-pump install all use the same trade, and four different bills. Get the customer type wrong and the rest follows. CIS does not sit on a private householder, reverse charge does not sit on a customer who is not VAT-registered, and a combi swap billed as "gas works" is how a dispute starts.

The short answer

A UK gas engineer invoice depends on who you are billing. Homeowner: standard invoice, VAT only if registered, 20% on an existing-dwelling boiler swap and 0% on a qualifying heat-pump install until 31 March 2027. Contractor: split labour and materials, show your UTR, and 20% CIS if verified (30% if not) on labour only. Landlord: bill the CP12 check and attach the gas safety record separately.

Who are you billing? Three jobs, three invoices

Most "gas engineer invoice template UK" pages treat every customer as a name and a total. On the van they are not. A contractor working for a homeowner is still a contractor, and there is no reverse charge on a private customer. Homeowners only: skip CIS and reverse charge, but still read the stages, the tax point and Notice 708/6.

	Homeowner boiler service / swap	Landlord CP12 / gas safety record	Contractor heating or heat-pump package
Typical job	Annual service, breakdown, like-for-like combi swap, radiator or controls on a lived-in house	Annual landlord gas safety check on appliances and flues the landlord owns	New-build heating first-fix, full system install, residential heat-pump supply-and-fit
CIS on this invoice	No. An ordinary householder is not a CIS contractor.	Do not blindly print CIS. A landlord gas safety inspection is a record of inspection, not the installation of a heating system.	Often yes if they pay you as a subcontractor for installation of a heating system. Isolated boiler replacement as a component can sit outside. Detail below.
VAT if you are registered	Charge the right rate. Ordinary gas boiler work is usually standard-rated 20%. A qualifying heat-pump install in residential accommodation can be 0% until 31 March 2027.	A CP12 inspection is not the 0% energy-saving installation relief. Default existing-dwelling work is 20% unless a listed relief applies.	Often domestic reverse charge on standard- or reduced-rated CIS construction. 0-rated ESM install is not reverse charge.
How they want the bill	WhatsApp, same thread as the quote and the photo of the flue	Email or portal to the agent or landlord, with the record attached	Email to accounts, purchase order, site and plot ref
What bounces it	"Gas works", no appliance, no address, VAT at 0% on a gas combi	Invoice with no record attached, or the invoice pretending to be the CP12	Missing UTR, labour mixed with the boiler, no PO, reverse charge on a 0% heat pump

What must be on a UK gas engineer invoice?

GOV.UK is narrower than most blogs. You must give a VAT invoice by law when both you and the customer are VAT-registered. If you are not, keep numbered records of what you charged, which is also how you get paid.

• A unique identification number
• Your name (or company name), address and contact information
• The customer's name and address
• A clear description of what you are charging for
• The date the goods or service were provided (supply date) and the date of the invoice
• The amount being charged, the VAT amount if applicable, and the total amount owed

Sole trader with a trading name: show your own name and a serviceable address. Limited company: registered name, company number and registered office. The VAT registration threshold is £90,000, not the stale £85,000 figure. For a gas engineer, a clear description is what gets you paid, so name the address, appliance and stage.

By law, businesses carrying out gas work in the UK must be on the Gas Safe Register. You can put your Gas Safe number in the header if you hold it, but the invoice is not the certificate. A landlord gas safety record, often called a CP12, is a separate PDF: attach it to the bill, do not pretend the invoice is the record.

Labour versus materials: boiler, flue, copper and call-out

On a homeowner invoice the split is courtesy. On a contractor invoice it is the CIS calculation. Start with the gross, take off VAT, consumable stores, fuel (not travelling), plant hired for that job and materials you paid for directly. What is left is the CIS base at 20%, 30% or 0%.

Materials are what you paid for this job: boiler, flue kit, condensate pipe or pump, copper, fittings, radiators, cylinder or heat-pump outdoor unit. Mark-up stays in the labour base. Free-issue kit from the main contractor is not yours, and neither is a boiler the customer bought from a merchant. Call-out is labour, not a materials line and not a way to shrink CIS.

Line type	What belongs there	What does not
Labour	Call-out, diagnosis, strip-out, pipework, flue, commission, service, CP12 inspection time, heat-pump install hours	A mark-up you wish was copper
Materials	What you paid this job: boiler, flue, condensate, copper, radiators, cylinder, heat pump, merchant tickets on file	Free-issue kit, a customer's own boiler, van stock you did not buy for this address
Hire	Third-party scaffold, tower or lifting kit for this address, ticket on file	A notional hire on tools and a flue analyser you own
Variation	Agreed extra radiator, condensate pump, magnetic filter or extra pipe run, coded V01, V02	A silent bump inside "additional gas works"

Two habits cost money: one lump "boiler replacement £4,000" (20% of the appliance as well) and stuffing mark-up into materials so CIS looks smaller. Van stock used on the job can sit in materials if you can show what it cost. Guessing a round figure is how a contractor estimates against you.

VAT on gas boilers, heat pumps and servicing

If you are not VAT-registered, do not charge VAT. If you are registered, the rate is not "heating equals 0%". Under VAT Notice 708/6, a qualifying heat-pump install in residential accommodation is 0% until 31 March 2027, then 5% from 1 April 2027. Supplying the materials without installing them is always standard-rated.

Do not claim 0% on a gas combi swap. A conventional boiler with radiators, pipe, valves and controls is a single standard-rated 20% supply. Energy-efficient boilers are standard-rated unless the grant-funded rules in section 3 apply. Servicing and repair of any energy-saving material is not the 0% installation relief, so default existing-dwelling work is 20%.

Job	VAT rate if you are registered
Gas boiler service or breakdown on an existing dwelling	20%
Conventional combi swap with radiators and controls (Notice 708/6 Example 2)	20%
Air, ground or water source heat-pump install in residential accommodation	0% until 31 March 2027, then 5%
Heat pump or boiler supply without installation	20%
Grant-funded boiler install to a qualifying person (Notice 708/6 section 3)	5% on the grant-funded part
Landlord CP12 / gas safety inspection	20%
Domestic reverse charge on standard- or reduced-rated CIS work	Show VAT, do not add it to the amount they pay
0-rated ESM install under a contractor	Not reverse charge

How do CIS deductions work on a boiler, flue and copper?

CIS covers installing systems for heating, lighting, power, water and ventilation. You invoice the contractor the gross, and they withhold from labour as an advance on your tax and NI. The rates are 20% if you are verified, 30% if you are not and 0% if you have gross payment status.

CIS is on labour only, including call-out. The boiler, flue, condensate and copper you paid for come off the gross. Heating and plumbing have a wrinkle generic blogs skip: HMRC treats installation of a system as in scope, while repairing, maintaining or replacing a boiler as a component of an existing system can sit outside if that is all the contract is. A landlord gas safety inspection is a record of inspection, not the installation of a heating system, so do not blindly print CIS. InvoiceAdept does not decide CIS status.

Show UTR, labour, materials, rate, deduction and net payable on the invoice. That printout is not a CIS300, and the contractor files it. InvoiceAdept does not file CIS300.

Stage payments for boiler and heat-pump supply-and-fit

A Saturday service is one invoice. A boiler or heat pump you have to order is not. Name the stage on every bill and match your quote.

1. Deposit: before you order the boiler, flue, cylinder or heat pump. Invoice when you take it and state the percentage.
2. Delivery or first fix: kit on site, pipework, or the outdoor unit positioned.
3. Commission or practical completion: appliance live, records issued, balance less any agreed retention, plus variations approved in writing.

Retention is not a deposit. Deposit is money you take before or during. Retention is money held after completion against snagging. Show full value, retention withheld and release date, then invoice retention when it falls due. A deposit you receive is a VAT tax point for that amount on the day it lands if you are registered, and a doorstep card payment on a breakdown is usually a tax point that day.

Making Tax Digital for income tax

If your qualifying income is over £50,000 for 2024 to 2025, Making Tax Digital for Income Tax applies from 6 April 2026. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028. Qualifying income is turnover before expenses, so use HMRC's checker rather than a blog.

InvoiceAdept keeps digital invoice records you can export for an accountant or HMRC-recognised filing software. It does not submit quarterly Income Tax updates, the Self Assessment return, your VAT return or CIS300. Records are not filing (gov.uk Making Tax Digital for Income Tax guidance).

Mileage and van expenses

Mileage is a Self Assessment question, not an invoice line, but it matters to a gas engineer. For a car or van you use for business you can claim HMRC's approved mileage rate: 45p a mile for the first 10,000 business miles and 25p a mile above that, instead of tracking every fuel and repair receipt. Van mileage works the same way, and the simplified rate is often your net daily van cost. Tools, Gas Safe registration and training are expenses too, but they belong on your tax return as allowable expenses, not as a fake materials line on a customer invoice.

How to send it, and how InvoiceAdept fits

Domestic jobs sold in WhatsApp: put the invoice in that thread. Contractors: email accounts with the purchase order. Landlords: invoice plus the gas safety record as two files. Put bank details or a card link on every invoice, and a clear due date. "Payment due on receipt" is vague, "due 8 September 2026" is a date.

InvoiceAdept is invoicing software for UK trades. Free is five invoices a month, Pro is £7.99 a month excluding VAT with WhatsApp send and Stripe at no extra platform fee, and Pro+ at £12.99 adds CIS. Invoicing features · CIS invoices · pricing. See how it fits on the gas engineers trade page.

FAQs

What should a UK gas engineer invoice include?

Legal names and addresses, a unique number, dates, a description that names the address, appliance and stage, quantities and rates, a due date and a way to pay. Split labour and materials. VAT only if registered and reverse charge does not apply. UTR and CIS only under a contractor, and only when CIS actually applies.

Do gas engineers need a CIS invoice?

Only when a contractor is paying you for construction operations. Installing a heating system as a system is typically in. Many repairs and a boiler replaced as a component can be outside CIS if that is all the contract is. A homeowner job you sold yourself: no CIS. A landlord CP12: do not blindly print CIS.

How do CIS deductions work on a boiler, flue and copper?

CIS is on labour only, including call-out. The boiler, flue, condensate and copper you paid for come off the gross. The rates are 20% verified, 30% unverified and 0% with gross payment status. A mark-up is not a material, and free-issue kit is not your material.

Do I charge 0% VAT on a gas boiler replacement?

Usually no. Notice 708/6 treats a conventional boiler with radiators, pipe, valves and controls as a single standard-rated 20% supply. Energy-efficient boilers are standard-rated unless grant-funded section 3 applies.

Do I charge 0% VAT on a heat-pump install?

If you are VAT-registered and installing an air, ground or water source heat pump in residential accommodation, yes: 0% until 31 March 2027, then 5%. Supply without install is 20%. Servicing and repair is not the install relief, so default to 20% on existing dwellings.

Does InvoiceAdept file CIS, VAT or Making Tax Digital to HMRC?

No. It raises the invoice, stores the record and on Pro+ prints CIS. It does not file CIS300, VAT returns or MTD quarterly updates.

The bottom line

Name the address, appliance and stage, split labour from materials, and bill the rate that actually applies to this job. That keeps a contractor's 20% CIS off your boiler, keeps a 0% heat pump from being reverse-charged, and keeps a landlord CP12 attached as a separate PDF. Start free in 30 seconds.