Gas Safe registration: the ACS route, what it really costs, and the five-year clock

Every other ticket in UK construction is a contract term. A main contractor asks for a CSCS card because Build UK's site rules say so, not because Parliament does. Gas is the exception, and the exception is total: work on a gas fitting without being on the Gas Safe Register and you have committed a criminal offence, and in 2026 people are being sentenced in the Crown Court for it.

That is why this is the hardest gate in the trades and the most valuable ticket to hold. Roughly 80,000 businesses and more than 150,000 engineers are on the register, and the barrier that keeps the number there is the same barrier that keeps your day rate up.

This page is the whole route: the certificates, the codes, the money, the annual renewal, and the five-year clock that quietly decides whether you keep working.

What CORGI became, and what you are actually joining

CORGI ran gas registration for decades and the name still turns up on customer paperwork. The statutory function moved on 1 April 2009, when the Gas Safe Register launched across Great Britain and the Isle of Man. Northern Ireland and Guernsey followed on 1 April 2010.

The register is not a government department. It is run under a services concession agreement with the Health and Safety Executive by Capita Gas Registration and Ancillary Services Ltd. HSE awarded the original ten-year contract on 8 September 2008, a further agreement ran from 1 April 2019, and after a competitive tender HSE awarded Capita a new contract worth £89 million running from April 2025 to December 2029.

The practical consequence of that structure is worth holding on to. HSE writes the law and approves the class of persons. Capita operates the list, checks the competence, issues the cards and takes the fee. When people complain about the fee they are complaining to a contractor, and when people are prosecuted they are prosecuted by HSE.

The law, in three lines of one regulation

Everything on this page hangs off regulation 3 of the Gas Safety (Installation and Use) Regulations 1998.

Regulation 3(1). "No person shall carry out any work in relation to a gas fitting or gas storage vessel unless he is competent to do so."

Regulation 3(3). "No employer shall allow any of his employees to carry out any work in relation to a gas fitting or service pipework and no self-employed person shall carry out any such work, unless the employer or self-employed person ... is a member of a class of persons approved for the time being by the Health and Safety Executive." The approved class is the Gas Safe Register. That single sentence is the whole legal basis for registration.

Regulation 3(7). "No person shall falsely pretend to be a member of a class of persons required to be approved." Using the Gas Safe logo when you are not on the register is its own offence, separate from the gas work itself.

Sitting alongside them, regulation 5(3) requires that work on a gas fitting or gas storage vessel is carried out "in accordance with appropriate standards and in such a way as to prevent danger to any person". That is the regulation prosecutors add when the work was not just unregistered but bad.

Two 2026 cases show what the courts do with this.

On 23 July 2026 at Portsmouth Crown Court, Bradley Willis-Chambers, 47, was sentenced for illegal boiler installations at two Hampshire properties carried out while unregistered. He was struck off the register in 2016 for failing to demonstrate competence. The sentence was 18 months' imprisonment suspended for two years, 180 hours of unpaid work, £600 compensation to each of four victims, and a victim surcharge. The counts were under regulations 3(3) and 5(3).

Nine days earlier, on 14 July 2026 at South Tyneside Magistrates' Court, Alexander Robson, 38, was sentenced over ten breaches after advertising gas work on Facebook and flyers using the Gas Safe logo while unregistered, and working on boilers, gas fires and pipework at five homes. He received eight months suspended for two years, a six-month mental health treatment requirement, 30 days of rehabilitation activity, £450 compensation and £200 costs. HSE Inspector Darian Dundas put it plainly: "These breaches were carried out brazenly and in the open using social media and faking the Gas Safe logo to tout for business."

Both routes were used in the same month, magistrates' court and Crown Court, which tells you the offence is triable either way and that custody is genuinely on the table. Nothing else in the UK trades behaves like this.

ACS: the certificates that make you competent

The route to the register runs through the Accredited Certification Scheme, universally called ACS. It is an assessment scheme rather than a course. You are not taught and then passed; you are examined, in a centre, on written papers and on live rigs, and the certificates you walk out with define exactly what you are allowed to touch.

The scheme is modular. One core certificate is compulsory, and every appliance you want to work on is a separate module bolted to it.

The distinction people miss is that CCN1 on its own puts you nowhere near a boiler. It is the safety core: it proves you can test a system, size a flue and make a property safe. CENWAT is what lets you install and service the boiler the customer actually rang you about. A registration carrying CCN1 and CENWAT is a working domestic heating engineer. A registration carrying CCN1 alone is not.

Category by category is also how the register polices you. Your ID card lists the categories you hold, and a landlord's gas safety record signed for an appliance outside your categories is work you were not qualified to do.

Starting from nothing: the managed learning programme

There is no requirement to serve an apprenticeship. For an adult career changer the standard route is a managed learning programme, run by an approved centre against an awarding organisation's specification such as LCL Awards, followed by a supervised portfolio, followed by ACS.

It runs in three stages, and the middle one is where the timeline really sits.

Stage one, the training. Classroom and workshop, covering gas safety legislation and standards, pipework installation, appliance servicing, heating controls and combustion analysis. A new entrant with no plumbing background is looking at roughly 8 weeks full time, Monday to Friday. The same content delivered on alternate weekends stretches to something closer to 40 weeks. Someone arriving with a Level 2 plumbing qualification or three or more years of verifiable plumbing experience takes a shorter programme, around six weeks, because the pipework and water side is already there.

Stage two, the portfolio. This is the gate that surprises people, and it is the reason gas cannot be bought in a fortnight. You have to evidence real gas work carried out under the supervision of a Gas Safe registered engineer, signed off with their licence details: installations, services, safety inspections, gas escapes, tightness testing, combustion analysis. A minimum of six months must pass after your training before you can sit ACS, and the portfolio window runs for two years. If you have an employer, this stage costs you nothing but time. If you do not, training centres sell brokered placements, typically around £1,495 including VAT.

Stage three, ACS. Five days at an assessment centre for the core and CENWAT. Pass, and you hold certificates. Certificates are not registration; they are what registration is granted on.

One further constraint shapes year two. The additional appliance categories, CKR1, HTR1, MET1 and DAH1, are generally taken 12 months after you are registered, once you have real appliance work behind you. Plan your first year around boilers, and widen afterwards.

Registering the business, registering the engineer

The registration is held by the business, not by the individual. A sole trader registers as a business of one. A limited company registers as the company. Each engineer who works under that registration is separately registered against it and issued their own ID card, so a firm with four engineers holds one business registration with four engineers attached.

Applying means submitting the business details, your ACS certificates, and evidence of the working practices and equipment behind them. Capita then carries out a competence check, and it is a real inspection rather than a form: the register runs more than 55,000 competence checks a year, and initial registration inspections are part of that number.

The ID card is the visible end of it. The front carries your photograph, your name, your licence number and the card's expiry date. The reverse lists the gas categories you are registered for, which is what a diligent landlord or letting agent reads before letting you touch anything. The physical card has carried raised numbers and braille dots for customers with sight loss, and Capita has announced a digital Gas Safe licence card to sit alongside it, so verification is moving the same way CSCS Smart Check moved site cards.

Registration is renewed annually. The registration year runs from 1 April to 31 March, and the fee is set by the register for each year. For the year to 31 March 2027, business renewal is £167.74 including VAT online and £205.90 including VAT by phone or post. Renewing online rather than on paper saves £38.16 for filing the same renewal a different way. One engineer is included in that renewal, and each additional engineer on the registration is £53.28 including VAT.

What the fee buys, and what engineers say about it

The fee funds the register's operations: the competence checks, the public search, the complaints and investigations function that struck Willis-Chambers off in 2016, around 200,000 calls a year from engineers and the public, and more than 3.5 million website visits in 2023/24. It also funds the thing that makes your registration worth holding, which is enforcement against the people undercutting you.

It is not a popular bill. When the 2025 rise landed, heating engineer Andy Gibbs, writing in the trade press, was blunt:

"We are being taken for mugs here, a hundred thousand milch cows who Capita can rinse for a bit of easy money."

Andy Gibbs, on the Gas Safe registration fee rise, Installer

He is arguing about value for money, and that argument is worth having. The arithmetic underneath it is less arguable. Spread across a year of domestic heating work, the renewal is a fraction of a single boiler swap, and it is a tax deductible business expense for a self-employed engineer, which HMRC has confirmed. If you have never costed what an hour of your time has to earn to cover fixed overheads like this one, what an hour actually costs you does that sum properly.

The five-year clock, and the twelve-month cliff

ACS certificates run for five years. Registration runs for one. Losing track of either one is how competent engineers end up off the register.

Reassessment before expiry is quick and comparatively cheap, because the scheme treats you as an experienced operative rather than a new entrant.

That bottom row is the cliff. Twelve months and a day after expiry, the reassessment route closes and you go back through initial assessment as though you had never held the certificate. A domestic engineer with core plus four appliances who reassesses on time pays £795. The same engineer who lets it drift past the twelve-month line pays £700 for the core and £150 for each of four appliances, which is £1,300, plus the lost work while it is arranged.

Assessment centres also allocate a full five-day block and require full re-payment if you fail and rebook, so the reassessment week is not a week to walk into cold.

Put the two clocks in the same diary. The annual renewal falls on the registration year, and the five-year ACS date falls whenever your certificates were issued. Set the ACS reminder for four years and nine months, not five years, so a booked-out centre in your area cannot push you over the line.

Domestic, commercial and LPG are three separate stacks

The word "gas" hides three different qualification ladders. Holding one of them says nothing about the other two.

Domestic is the CCN1 ladder above: dwellings, domestic appliances, the appliances people have at home.

Commercial starts again with its own core. An engineer already holding domestic ACS and registered for more than 12 months crosses over via CODNCO1, the changeover core, rather than sitting COCN1 from scratch. The commercial modules are appliance-and-plant shaped rather than boiler-and-fire shaped.

A three-week changeover package covering CODNCO1, ICPN1, TPCP1A, CIGA1, CDGA1 and CORT1 runs around £1,995 including VAT. The five-day commercial reassessment, for an engineer whose commercial ACS is expiring or lapsed under 12 months, runs around £1,250 including VAT. Commercial catering, laundry and metering are further ladders again.

LPG is not a separate core. It is a changeover from whichever core you already hold, which is why the pricing looks so different. CONGLP1 requires a valid core gas safety certificate already in hand, whether that is CCN1, COCN1 or CCCN1, and then the LPG-specific environments are individually priced modules.

For anyone working off the mains gas grid, and for anyone near a caravan park, a marina or a park home site, LPG is the cheapest scope extension in the whole scheme. A £456 including VAT changeover opens a category of work that sits outside the scope of an engineer holding CCN1 alone.

Two costed routes, end to end

Route one: standing start, no trade background, to registered domestic heating engineer.

Elapsed time, honestly stated: eight weeks of training, then a portfolio stage of at least six months, then a five-day assessment week. Call it eight to twelve months from the first classroom day to the card in your hand, and about twenty months to a full domestic category set. An employed trainee whose employer provides the portfolio work removes the £1,495 and often the training cost with it.

A plumber arriving with Level 2 or three years of evidenced experience takes the shorter programme at around £3,195 including VAT and skips the pipework relearning, which is the single biggest saving available to anyone already in the trade.

Route two: an established engineer at the five-year mark.

That is the number to keep in your head when somebody tells you gas registration is expensive. Roughly £327 a year is the standing cost of a licence that is a criminal offence to work without, in a trade where the register holds roughly 80,000 businesses and 150,000 engineers. Add commercial and you are at about £577 a year. Add LPG and it moves by about £91 a year.

Where the money genuinely goes is year one, and it is a training bill, not a registration bill.

What it costs

Gas Safe registration is paid to the register, once a year, and nothing on AEC Stack changes that. What the platform does is make sure the two clocks and the money behind them are somewhere you will see them.

There is no monthly subscription. The platform fee is 2.5% of each invoice processed through AEC Stack, taken when the invoice is paid, so a quiet month costs nothing and a training month costs nothing. Your ACS expiry, your registration renewal date and your public liability renewal sit against the business rather than in a drawer, and your training and assessment invoices land in the same place as the jobs they made possible, which is what makes them straightforward to claim at year end.

Put your ACS expiry date and your renewal date in one place, four years and nine months apart, and see what your year one training bill looks like against the work it unlocks: start with the business.