Gas Safety Certificate (CP12) Explained for Landlords

The gas safety certificate — properly called a Landlord Gas Safety Record, and still widely known by its old form number, CP12 — is the one landlord document with no wriggle room. It's an annual legal requirement wherever a rented property has gas, and the penalties for getting it wrong sit at the serious end of the scale, because the risk it guards against is carbon monoxide poisoning and gas explosion, not paperwork tidiness.

Who needs one

If you let residential property with any gas appliance, fitting or flue — a gas boiler, gas hob, gas fire, or even just a capped supply serving an appliance — you need a gas safety check every 12 months, carried out by a Gas Safe registered engineer. Not "a qualified plumber", not "the chap who's always done it": Gas Safe registered, and you can verify any engineer's registration and qualifications on the Gas Safe Register before they touch anything.

Appliances the tenant owns are outside the check itself, but flues and pipework serving them are still yours.

The annual cycle and the 28-day rule

Two deadlines matter:

• Every 12 months: a new check before the old record expires. Usefully, if you have the check done in the final two months of the current record's life, the renewal date is preserved — so servicing early doesn't shorten your year, and you should never be tempted to run late "to get full value".
• Within 28 days: a copy of the new record must go to every existing tenant within 28 days of the check. New tenants must receive the current record before they move in.

That second rule is where organised landlords quietly fail. The check gets done, the engineer leaves the paper record on the boiler, and nobody sends the tenant a copy. If it's ever disputed, "the tenant had access to it" is not the same as "the tenant was given it" — send it by email so the delivery dates itself, or get a signed acknowledgement for paper copies.

Failing on gas safety is a criminal matter under the Gas Safety (Installation and Use) Regulations, with unlimited fines and imprisonment available in the worst cases — and an unserved gas safety record can also derail possession proceedings.

What the engineer actually checks

A gas safety check is an inspection, not a service (though many landlords sensibly book both together). The engineer will:

• Test each appliance's operation — burner pressure and heat input against the manufacturer's specification
• Check flues and chimneys — that combustion products are being carried safely outside, with flue flow and spillage tests
• Check ventilation — that each appliance has the air supply it needs to burn safely
• Inspect the installation — pipework tightness test, condition of fittings, that appliances are stable and correctly connected
• Check safety devices — flame supervision devices and cut-offs work

The record lists each appliance, what was checked, any defects found and the action taken. If something is unsafe, the engineer will classify it — "Immediately Dangerous" (ID) or "At Risk" (AR) — and may disconnect the appliance with your or the tenant's agreement. Fix defects promptly and keep the remedial invoice with the record: a defect noted and repaired, with evidence, is a compliance story; a defect noted and ignored is a prosecution exhibit.

Keeping records properly

The legal minimum is to keep each record for two years. Keep them all anyway:

• A complete run of CP12s proves a continuous safety history if anything is ever alleged
• Buyers and their conveyancers increasingly ask for gas service history when you sell
• Insurers may want evidence after any gas-related incident

Practical habits: photograph or scan the record the day of the check, store it against the property (not in a general email inbox), diary the renewal for month ten or eleven so the two-month preservation window works for you, and log the date you sent the tenant their copy.

The CP12 is one of several certificates on annual and multi-year cycles — the EICR, alarms, EPC and deposit rules all have their own clocks. Our landlord compliance checklist puts the whole set in one place.

If juggling those dates across one property or twenty is the pain point, HomePassport for landlords stores each CP12 against the property and reminds you before the twelve months — and the 28-day window — run out.