Checked 21 October 2026. Rules from IGEM's Assessment page, Guidance Note 8 v8.1 and Gas Safe Register pages read 21 Oct 2026. How early you may renew, and assessment fees and dates, are not stated in the sources quoted here; ask your certification body or centre.
An ACS certificate is not a lifetime qualification. IGEM, which manages the industry's Standard Setting Body, says: "Gas Safe Registered engineers are required to renew their certificates of competency every 5 years, and this can be done either by ACS renewal or via the Group Competency Scheme." Gas Safe Register says the same from its side: "Certificates of Gas Safety Competence are renewable every five years. Gas Safe Registration is renewable annually."
IGEM Assessment page, Guidance Note 8 v8.1, Gas Safe Register renewal and overseas-applicant pages, read 21 Oct 2026.
Two clocks, not one
There are two renewals. Your certificates of competence (CCN1, CENWAT and the rest) run for five years and are renewed by assessment. Your business's Gas Safe registration runs for a year and is renewed with Gas Safe Register. The second depends on the first: on its renewal page Gas Safe Register says "In order to renew your registration you must have a valid core qualification – CCN1 or COCN1." It adds that you "must have up-to-date qualifications for the categories of work that you carry out."
| What | Renewed every | Renewed by | Who issues it |
|---|---|---|---|
| Certificate of gas safety competence | 5 years | IGEM: "either by ACS renewal or via the Group Competency Scheme" | For ACS, your certification body |
| Gas Safe registration | 12 months | Renewal with Gas Safe Register, online or by post | Gas Safe Register |
What lapses when the core lapses
Gas Safe Register's Registration Policy (v9.0, February 2026) says each engineer's licence card shows "a list of work categories with end dates that correspond with the expiry dates of core certificates of gas safety competency." In other words, the end date printed against a category such as "Gas Boilers" is your core certificate's expiry date, not your CENWAT's.
The policy also says what happens when a certification body reports a failure: "registration of any relevant work categories will be suspended. Registration may be affected if this involves a core competence." And a business needs "a minimum of one engineer, holding current certificates of gas safety competence" listed against it, and a business with no listed engineers automatically has its status changed to "not registered".
Gas Safe Register has been plain about this before. In guidance updated on 19 July 2021, during the pandemic, it said: "To maintain their Gas Safe registration, engineers must ensure that expired ACS qualifications are renewed." It also said engineers are expected "to take all reasonable measures to maintain their ACS qualifications, including planning ahead". That page was about the 2021 disruption; the current renewal page, quoted above, still requires a valid core qualification.
The two ways to renew
ACS re-assessment
- Guidance Note 8 (v8.1, from 1 Oct 2024) route 1: "Renewing an existing or expired ACS or GCS certificate" (or gas qualification) with an equivalent ACS certificate. Training: Optional.
- IGEM: "Training is not a pre-requisite for re-assessment but it is required for an extension to range or scope."
- The CCN1 re-assessment adds area 16, "Inspect, test, commission and maintain gas appliances (Re-assessment only)", and some ventilation items are knowledge and understanding at initial assessment but performance criteria at re-assessment.
- Area 16 of CCN1 covers HTR1, LAU1, WAT1, LEI1, CKHB1, HWB1 and DFDA1 appliances, and says: "For CENWAT, CKR1 & DAH1 Re-Assessment see individual ACS elements". CENWAT, CKR1 and DAH1 are re-assessed under their own modules.
Group Competency Scheme (GCS)
- Named by IGEM as the other renewal route. CCN1 Issue 20.1 accepts a "Group Competency Certificate" as a prerequisite for CCN1 re-assessment.
- Whether your employer runs a GCS, and what it covers, is a question for your employer.
Renewing and adding appliances are different things
Adding work is not a renewal; it is an extension. GN8 calls adding appliances in the same sector "Extend Range" (its example: "holding CCN1 & CENWAT adding HTR1") and moving sector "Extend Scope" ("Domestic to Commercial"). For both, training is required, and GN8 note 2 says engineers "must provide evidence to the centre that there has been a minimum duration of twelve months from completion of their qualification or core ACS"; the exception is an "MLP- Bridge" through a recognised training provider. Another stated exception: a CCN1 holder does not need the twelve months before training and assessment for MET1, REGT1 or CESP1/CMA1/CMA3.
GN8's Table 3 gives indicative durations (in a section headed "Guided Learning Hours") for existing Gas Safe engineers who extend their range. Its own note: "The durations are indicative and should not be considered as a minimum, maximum or fixed."
| Extension (GN8 Table 3) | Hours | Days |
|---|---|---|
| Domestic central heating and hot water appliances, CENWAT (with heating design, hot water safety and water regulations) | 31 | 4.5 |
| Domestic ducted air heaters (DAH1) | 7 | 1 |
| Domestic cooking appliances (CKR1) | 7 | 1 |
| Domestic space heating appliances (HTR1) | 7 | 1 |
| Installation of domestic meters (MET1) | 7 | 1 |
| Non-domestic and catering appliances (per appliance) | 7 | 1 |
From IGEM's Assessment page, Gas Safe's renewal page and Registration Policy v9.0, read 21 Oct 2026.
One certificate Gas Safe does not receive automatically
ACS results reach Gas Safe Register electronically from your certification body. Unvented hot water storage is different. Gas Safe's Registration Policy says that a business wanting to notify the installation and commissioning of unvented hot water storage vessels "must provide current evidence of competence separately, i.e., certificates of competence for unvented hot water storage vessels that have an expiry date of less than 5 years, as this evidence is not part of the gas competence (ACS) download process." When that certificate is renewed, the business has to send the new one to Gas Safe.
Before winter: a checklist
Make these checks well before your core certificate or your registration reaches its end date. The dates come from the official rules above; the questions to ask the centre are our suggestions:
Is your ACS renewal under control?
Tick what is true. Each unticked line is something to sort out before your diary fills up.
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We do not state how early a certificate can be renewed without losing time: none of the official pages we read sets that rule, so ask your certification body.
Try one question
You have just serviced a customer's gas boiler. Which of these is NOT one of the examinations regulation 26(9) requires immediately afterwards?
- A. The effectiveness of any flue
- B. The supply of combustion air
- C. The pressure gauge reading on the sealed heating system
- D. Its operation so as to ensure its safe functioning
Show the answer
C. Regulation 26(9) lists the flue, the supply of combustion air, the operating pressure or heat input (or, where necessary, both; or, where that is not reasonably practicable, the combustion performance) and safe functioning. The water pressure of the heating system is not one of them.
Our own question, written from the regulation quoted. It is not an ACS assessment question.
Frequently asked questions
How often do I need to renew my ACS?
Every five years. IGEM says Gas Safe registered engineers "are required to renew their certificates of competency every 5 years", by ACS renewal or the Group Competency Scheme.
Do I need training for ACS re-assessment?
Not for a straight renewal. Guidance Note 8 marks training as optional for renewing an existing or expired ACS certificate, and IGEM says training is not a pre-requisite for re-assessment. Training is required to add appliances or a new sector.
What happens if my CCN1 expires?
Gas Safe says you need a valid core qualification, CCN1 or COCN1, to renew registration, and the end dates of your work categories follow the expiry of your core certificate. Renew the core before it runs out.
Can I renew an expired ACS?
Guidance Note 8 route 1 covers "Renewing an existing or expired ACS or GCS certificate". Ask the centre what evidence it needs before booking if your certificate has already expired.
Is Gas Safe registration renewed every five years too?
No. Gas Safe registration is renewed every year. Only the certificates of competence run for five years.
ProSyllabus is an independent study site, not part of Gas Safe Register, HSE, IGEM or any ACS certification body. Rules here are quoted from the regulations and the scheme's own documents; ask your assessment centre how your own assessment will run.
Sources
- official — IGEM: Assessment, overview of Matters of Gas Safety, ACS and other routes to competence (read 21 Oct 2026)
- official — IGEM: ACS Entry Routes and Changeover Requirements, Guidance Note 8, version 8.1 (implementation 1 Oct 2024), linked from the Assessment page
- official — Gas Safe Register: How to renew your Gas Safe registration (read 21 Oct 2026)
- official — Gas Safe Register: Overseas applicants (read 21 Oct 2026)
- official — Gas Safe Register: Registration Policy, P001_REG001 v9.0, February 2026 (sections 5.2, 7 and 7.8)
- official — IGEM resource library: ACS.CCN1 Safety Assessment Criteria, Initial and Re-assessment, Domestic Natural Gas, Issue 20.1 (listed Oct 2026)
- official — Energy & Utility Skills: ACS Gas Assessment Centre Directory, Version 16, December 2025 (linked from IGEM's Assessment page)
- official — legislation.gov.uk: GSIUR 1998, regulation 26 (Gas appliances, safety precautions; 26(9)(ca) inserted 6 Apr 2018)
official = a document published by the conducting body. reported = a news or coaching site we could not check against an original. Where sources disagree this page says so rather than picking one.
