Most trade credentials are good signals. Gas is different: it is the one trade where the credential is a legal requirement, it has to be renewed every single year, and the card in someone's wallet can be out of date without anyone meaning harm. Gas Safe engineers renew their licence every year, and their qualifications every five years, so a registration that was real when you first hired someone can have lapsed by the time they come back. That is why this check is worth five careful minutes rather than a glance at a sticker.
The rule itself is short. In the Health and Safety Executive's own words: anyone employed to work on gas appliances in domestic premises must be a Gas Safe registered engineer and competent in that area of gas work. Underneath that sits the Gas Safety (Installation and Use) Regulations 1998, which put a competence duty on everyone and require any business doing gas work to be on the register that the HSE approves, which today is the Gas Safe Register. The register covers the UK, the Isle of Man, Guernsey and Jersey.
What the register's own investigators keep finding
A note on the numbers in this section: they are Gas Safe Register's and the Health and Safety Executive's published figures, not our own records, and we link every source at the end. The headline finding: approximately two thirds of the illegal gas work inspected by the Register has been found to be unsafe, according to the Register's current guidance. Bear the selection in mind, because these are jobs that worried someone enough to be reported and inspected, not a sample of all gas work. In the Register's 2017 research, one in five inspected appliances was so dangerous it had to be disconnected on the spot. And research the Register published back in 2016, based on interviews with 575 fitters who advertised in late 2014 and early 2015, estimated around 1.1 million gas jobs a year were being carried out by fitters who were not properly qualified.
The consequences are not theoretical. In October 2025, Chester Magistrates' Court sentenced Scott Anthony Williams for illegal gas work on two Cheshire properties between 2021 and 2023 while unregistered: seven breaches of the gas safety regulations, a gas leak among the results, and a gas safety certificate issued with a false registration number. He received a twelve month community order, 240 hours of unpaid work, and paid costs of 2,000 pounds plus a 144 pound surcharge. The Health and Safety Executive was alerted by the Gas Safe Register itself. The point of that story is not fear of tradespeople; it is the opposite. Registered engineers are the safe path, and the register exists so you can tell who they are.
The five minute check, done properly
Start on the official Gas Safe Register website, which lets you search by business name or check a number, free. One thing catches people out: there are two different numbers. The business has a registration number, and each engineer carries their own card with a unique seven digit licence number that changes every time a new card is issued. If you type a business number into an engineer lookup you will get a confusing blank, so match the number to the search. Our own Gas Safe number checker will point you at the official register to confirm whichever number you have; the official register is the definitive place to confirm anyone.
Then, on the day the engineer arrives, ask to see the ID card. The front carries the photo, the dates and the licence number. The part most people never look at is the back: it lists the work categories the engineer is actually qualified for, and qualified for boilers does not automatically mean qualified for your fire or your cooker, so check the category matches your job. Cards exist digitally now too, with a code you can scan and the categories a scroll away. Any registered engineer will hold the card up without blinking; they renew it every year precisely so it can speak for them.
Landlords have one extra job a year
If you rent out a property with gas appliances, the annual gas safety check is yours to arrange, and only a Gas Safe registered engineer can do it. The Health and Safety Executive's rules are specific: keep the record of each check for two years, give a copy to existing tenants within 28 days of the check, and give new tenants a copy before they move in. The document is called the Landlord Gas Safety Record, though you will still hear it called a CP12. One useful modern touch: you can have the check done up to two months before the deadline and keep your original renewal date, the same way an early MOT works.
If the work is already done
Maybe you have just read all this and remembered a boiler that was fitted cheaply two winters ago, or you have bought a house and the paperwork is thin. The flow below is the short version. If you can smell gas or anyone has symptoms, that is an emergency: call the gas emergency line on 0800 111 999 first, get fresh air, and turn the gas off if it is safe to. If there is no immediate danger but the work worries you, report it to the Gas Safe Register; they can arrange an inspection and send a report to the Health and Safety Executive, the authority that prosecutes. Either way, have a registered engineer look the work over properly.
Two pieces of paperwork matter afterwards. First, the money side: the Register's guidance notes that using an illegal gas worker could invalidate the warranty on your boiler and may invalidate your home insurance, which is worth knowing before you decide the cheap job was cheap. Second, for a new boiler or heating appliance in England and Wales, the registered installer is supposed to notify the local authority within 30 days, which produces a Building Regulations Compliance Certificate. That certificate belongs to the property, and it comes in useful when you sell or remortgage, so chase it now rather than at exchange. Scotland and Northern Ireland run their own rules.
The carbon monoxide safety net
Behind all of this sits the reason the law exists: carbon monoxide has no smell and no colour. Gas Safe Register lists six main symptoms of poisoning: headaches, dizziness, nausea, breathlessness, collapse and loss of consciousness. If you suspect it, get into fresh air, call the gas emergency line on 0800 111 999, contact NHS 111 about suspected poisoning, and call 999 or go to A and E if symptoms are severe. An audible carbon monoxide alarm near every gas appliance is the cheapest insurance in this whole piece.
Where we fit in
On our site, gas engineers' profiles show the register records we hold, each with the date we collected it and a link to the official register, which stays the definitive source. One honesty rule we build into everything, and it protects tradespeople as much as homeowners: if someone does not appear in the records we hold, that never means they are unregistered. Records lag, names vary, numbers get mistyped. The official register is the place to confirm, and our checker exists to get you there with the right number in hand.
Is it illegal to do your own gas work at home?
The law has two parts. The Gas Safety (Installation and Use) Regulations 1998 require anyone doing gas work to be competent, and they require any business doing gas work to be on the Gas Safe Register. So a business must be registered, full stop. For work in your own home the registration duty does not attach the same way, but the competence duty still applies to everyone, and in the Health and Safety Executive's words, anyone employed to work on gas appliances in domestic premises must be a Gas Safe registered engineer. Practically: hire registered, always.
Can my plumber also do the gas work?
Only if the business is on the Gas Safe Register and the engineer's card covers that category of work. Plumbing and gas are different qualifications, and plenty of excellent plumbers do not touch gas at all. Ask for the Gas Safe number, look it up on the official register, and check the back of the card for the work category that matches your job.
What does the back of a Gas Safe ID card show?
The work categories the engineer is qualified for, such as boilers, cookers or fires. Qualified for one category does not mean qualified for all of them, so the back of the card, or a scroll down on the digital card, is where you confirm the engineer is qualified for your specific job. The card also carries a photo, start and expiry dates, the engineer's seven digit licence number and the business's own registration number on the front.
Why might a genuine engineer's number not match the register?
Usually for mechanical reasons rather than sinister ones. The engineer's seven digit licence number changes every time a new card is issued, the business registration number is a different number entirely, and numbers get mistyped. Ask the engineer to show the card again, try the official register's search by business name, and give them the chance to clear it up. If it still does not resolve, the Gas Safe Register has a reporting route and can look into it properly.
Who can do a landlord's annual gas safety check?
Only a Gas Safe registered engineer. The landlord arranges it every twelve months, keeps the record for two years, gives existing tenants a copy within 28 days of the check, and gives new tenants a copy before they move in. The document is the Landlord Gas Safety Record, often still called a CP12, and the check can be done up to two months early without moving your renewal date.
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