Gas Safe Registration Explained
It is a legal requirement that anyone carrying out gas work in Great Britain is on the Gas Safe Register — and the usual route onto it is through ACS assessment in the categories of work you intend to do.
The Gas Safe Register is the official register of businesses and engineers who are legally allowed to carry out gas work in Great Britain and the Isle of Man. It replaced CORGI as the register in 2009, and by law anyone working on gas appliances, fittings or pipework must be registered for the categories of work they do.
This guide explains how registration works: the ACS (Accredited Certification Scheme) assessment route onto the register, how appliance categories work, the ID card and what it tells a customer, the legal position, and how registration is renewed. It is aimed at engineers understanding the route in and customers understanding what to check.
Key takeaways
- By law, anyone undertaking gas work in Great Britain must be on the Gas Safe Register for the categories of work they carry out.
- The standard route on is through ACS (Accredited Certification Scheme) assessment in the relevant categories, or an equivalent recognised qualification.
- Registration is category-specific: an engineer is only competent for the appliance types their assessment covers (e.g. domestic boilers, cookers, fires, LPG).
- Every registered engineer carries a Gas Safe ID card showing their registration, photo, licence number, start/expiry dates and the categories they hold.
- ACS certificates and registration are time-limited and must be renewed (reassessed) periodically to stay on the register.
What the Gas Safe Register is
Gas Safe Register is the official gas registration body for Great Britain, the Isle of Man and Guernsey, appointed to hold the register of legally registered gas businesses and their engineers. It took over from CORGI as the register in April 2009. Its role is to hold the register, issue ID cards, investigate reports of illegal or unsafe gas work, and run inspections.
Registration is held by the gas business, with individual engineers registered under it and each carrying their own ID card. A customer can check any engineer or business on the Gas Safe Register to confirm they are registered and for which categories.
The ACS assessment route
The usual way onto the register is through the Accredited Certification Scheme (ACS). ACS is a set of assessments, taken at an approved centre, covering core gas safety and then the specific categories of appliance and work the engineer intends to do. New entrants typically reach ACS via a managed learning programme (for example an NVQ/diploma in gas installation and maintenance combined with on-site experience) before sitting the assessments.
The core assessment (commonly CCN1 for domestic natural gas) covers the fundamental gas safety knowledge — tightness testing, gas rating, ventilation, flue checks, unsafe situations — and must be held alongside the appliance categories. Passing ACS in the relevant categories provides the certificate of competence that supports the business's registration.
Core plus categories
ACS is modular: a core gas safety assessment plus separate appliance categories. An engineer is only competent — and only shown on their card — for the categories they have actually passed, which is why the card must be checked against the job.
Appliance categories and what they cover
Registration and competence are category-specific rather than a single blanket qualification. Common domestic categories include central heating boilers and water heaters, cookers, gas fires and wall heaters, and there are separate categories for LPG, commercial work, meters and other specialisms.
This matters on site: an engineer qualified for domestic boilers is not automatically competent to work on a gas cooker or an LPG appliance unless they hold that category too. It is also why the annual landlord gas safety check must be done by someone competent in the specific appliance type being checked.
The Gas Safe ID card
Every registered engineer carries a Gas Safe ID card. The front shows the engineer's photo, name, licence number, and the card's start and expiry dates; the reverse lists the specific categories of gas work they are qualified and registered to carry out.
Customers are encouraged to always ask to see the card and to check the categories on the back cover the work being done — a boiler service should be done by someone carded for boilers. The card can be cross-checked against the Gas Safe Register online or by phone if there is any doubt.
Check the back of the card
The categories on the reverse are what matter: a valid card that only covers cookers does not qualify someone to work on a boiler. Match the category to the appliance before work starts.
Renewal and staying registered
ACS certificates of competence are time-limited and must be renewed by reassessment periodically (commonly on a five-yearly cycle for the ACS categories), and business registration with Gas Safe is itself renewed on its own cycle with the associated fee. Letting an ACS category lapse means losing competence for that category until it is reassessed.
Staying registered also means keeping up with the standards — changes to IGEM procedures, the Unsafe Situations Procedure, appliance and Building Regulations requirements — and cooperating with Gas Safe inspections. Working on gas while unregistered, or outside the categories held, is illegal and is exactly what the register exists to stop.
Frequently asked questions
Is Gas Safe registration a legal requirement?
Yes. In Great Britain it is a legal requirement that anyone carrying out gas work is on the Gas Safe Register for the categories of work they do. Working on gas unregistered, or outside the categories held, is illegal.
How do I get onto the Gas Safe Register?
The usual route is through ACS (Accredited Certification Scheme) assessment in the relevant categories — a core gas safety assessment plus the appliance categories you intend to work on — typically after a managed learning programme and on-site experience. The certificate of competence then supports the business's registration.
What is the difference between ACS and NVQ?
The NVQ/diploma is the vocational qualification and learning route; ACS is the certificate-of-competence assessment that actually underpins registration. New entrants generally complete a managed learning programme and then sit ACS to get carded.
Does one qualification cover all gas appliances?
No. Registration is category-specific. An engineer carded for domestic boilers is not automatically competent on cookers, fires or LPG unless they also hold those categories — which is why you should check the categories on the back of the ID card.
How often is registration renewed?
ACS categories are time-limited and must be reassessed periodically (commonly every five years), and business registration is renewed on its own annual cycle. Letting a category lapse removes competence for that category until it is reassessed.
From guidance to action
Related guides
CP12: The Landlord Gas Safety Record
What a CP12 checks, the landlord’s legal duties, and how to complete one correctly.
Gas Tightness (Let-By and Drop) Test Procedure
The let-by and tightness test for a domestic installation, and the permitted pressure drop.
The Benchmark Certificate and Boiler Warranties
What Benchmark is, how it protects the warranty, and completing it correctly at commissioning.
