Gas safety certificate (CP12): what it is, when it expires, and what happens if you forget

A gas safety certificate is the one piece of paper a landlord cannot let lapse. It is a legal duty, it expires every year, and unlike most compliance the deadline moves with each property and each check. Miss it and you are committing a criminal offence — not risking a fine on renewal, but breaking the law from the day it expires.

Here is what it is, when yours is actually due, and what happens if it slips.

What a CP12 actually is

"CP12" is the old form number that stuck. The proper name is a Landlord Gas Safety Record (LGSR). It is the document a Gas Safe registered engineer gives you after inspecting the gas appliances, pipework and flues in a property you let.

The duty comes from the Gas Safety (Installation and Use) Regulations 1998. It is not best practice or a warranty condition — it is the law for anyone letting residential property with gas in England, Scotland and Wales (Northern Ireland has its own equivalent regulations).

The engineer checks that each appliance is burning correctly, that flues carry fumes safely away, and that there are no dangerous installations. The record lists what was checked and whether it passed.

Who needs one

You need a gas safety record if you let a property — a flat, a house, a room in an HMO — that has any of:

• a gas boiler, fire, cooker or hob you provide;
• gas pipework;
• a flue serving a gas appliance.

It covers the appliances and flues you are responsible for as the landlord. An appliance the tenant owns and brought with them is generally their concern — but the pipework and flue serving it usually are not.

If there is genuinely no gas at the property, there is nothing to certify.

When it expires — and the trap

The check must be done every 12 months. The record shows the date of the check; twelve months later, it is out of date.

The trap is that the deadline is per-property and easy to lose track of across a portfolio — and no one sends you a reminder. There is one helpful rule, though:

So you can safely book the engineer in the 10th or 11th month without shortening your own deadline. Leave it later than that and you are gambling on an engineer's availability.

The 28-day rule: giving it to tenants

Doing the check is only half the duty. You must also give the record to your tenants:

• to existing tenants, within 28 days of the check;
• to new tenants, before they move in.

Keep each record for at least two years. In practice you want them for longer — the history matters if an appliance is ever questioned.

A gas safety check is not a boiler service

This catches people out. A gas safety check confirms an appliance is safe right now. A boiler service is the manufacturer's maintenance that keeps the appliance working well and, usually, keeps the warranty valid.

They are different jobs, often on different clocks, and one does not cover the other. A boiler can pass a safety check and still be overdue a service that its warranty depends on — and vice versa.

What happens if you forget

Gas safety is enforced by the Health and Safety Executive (HSE). Letting a property with an expired or missing record is a criminal offence, prosecuted by the HSE, carrying unlimited fines and, in the most serious cases, imprisonment.

Beyond the law, a lapsed record can invalidate insurance, and — the reason the rule exists — an unchecked gas appliance is how carbon monoxide kills. This is the deadline you keep even when everything else waits.

Keeping on top of it

The hard part isn't the check; it's remembering the date on every property, every year, before an engineer's diary fills up.

When your record is renewed, photograph it. KeepUp reads the check date, files the record against the property, and reminds you in good time for the next one — so the anniversary never sneaks up on you. See how it works — it’s free for one place.