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ACS reassessment: the 5-year cycle explained

ACS is the Nationally Accredited Certification Scheme for Individual Gas Fitting Operatives. It's one of the recognised routes to the certificates of competence you need to be on the Gas Safe Register (NICEIC).

Checked 21 Oct 2026. Always read your certification body's current scheme rules.

The key dates

• Every 5 years: Gas Safe registered engineers renew their certificates of competence, by ACS renewal or through the Group Competency Scheme (IGEM). ACS certificates are normally valid for 5 years (BPEC).
• Up to 6 months early: BPEC says you can take the reassessment up to 6 months before expiry "without losing out" (MOT style). NICEIC also offers MOT-style certification under its scheme rules.
• More than 12 months expired: BPEC says you'll need the initial assessment instead of a reassessment.

How the assessments fit together

You take a core gas safety assessment first, then the appliance assessments for the work you do (NICEIC, BPEC). For domestic natural gas, NICEIC lists:

• Core: CCN1 (mandatory), listed together with combustion performance analysis (CPA1)
• Central heating boilers and water heaters: CENWAT
• Cookers: CKR1 · Gas fires: HTR1 · Meters: MET1 · Warm air heaters: DAH1

Changeover assessments let you move into another sector (for example domestic to non-domestic) without repeating the same work (NICEIC).

Training: when you need it

IGEM says training is not a prerequisite for reassessment, but you do need it before extending your range or scope. BPEC says assessments are usually a mix of practical and theory exams, and the certification body uploads your results to Gas Safe Register.

Bring your old certificates

BPEC says previous certificates must be shown to the assessment centre as evidence that you held the qualification.

What it costs

Each assessment centre sets its own prices. We haven't verified any yet, so we don't list figures. IGEM publishes an ACS Gas Assessment Centre Directory to help you find centres to ask.

While you're renewing: IGEM/UP/1B Edition 4 came into force on 1 October 2026, so expect tightness testing to the new procedure. See also Gas Safe fees 2026/27.

How often do gas engineers need ACS reassessment?

Every 5 years. IGEM says Gas Safe registered engineers must renew their certificates of competence every 5 years, either by ACS renewal or through the Group Competency Scheme.

How early can I take my ACS reassessment?

BPEC says reassessment can be taken up to 6 months before the expiry date without losing out ("MOT style"). Check your certification body's scheme rules.

What if my ACS has expired?

BPEC says that if an assessment element has expired by more than 12 months at the assessment date, you need to take the initial assessment instead of the reassessment.

Do I need training before ACS reassessment?

Not necessarily. IGEM says training is not a prerequisite for reassessment, but it is required to extend your range or scope. BPEC says applicants who meet the prerequisites do not need refresher training, though they may choose to take it.

How much does ACS reassessment cost?

Prices are set by each assessment centre and vary. GasStack has not yet verified centre prices, so we don't list any. Ask two or three centres for the total, including any refresher training you want.

Sources (checked 21 Oct 2026)

1. IGEM: Assessment (MoGS, ACS and other routes to competence)
2. BPEC: ACS
3. NICEIC: ACS Scheme

GasStack is an independent directory, not a training provider or certification body. This page summarises public sources and is not a substitute for the standards themselves or your training. Spotted something out of date? Tell us.