The Landlord’s Guide to Gas Safety Certificates (CP12)

If you let a property with any gas appliance, you have a legal duty to keep it gas safe — and the certificate that proves you’ve done so is the CP12, or Landlord Gas Safety Record. It’s one of the most important pieces of compliance in the rental sector, and one of the most commonly misunderstood. This is a plain-English guide to what a CP12 is, what it covers, how often you need one and what happens if you let it lapse.

What a CP12 actually is

A CP12 (Landlord Gas Safety Record) is a certificate issued by a Gas Safe registered engineer after they’ve checked the gas appliances, fittings and flues in a rental property. It confirms that each appliance has been inspected and is safe to use. The "CP12" name is a hangover from an old form number, but it’s still what most landlords and agents call it. It is not the same as a boiler service — though the two are often, and sensibly, done together.

What the law requires

Under the Gas Safety (Installation and Use) Regulations 1998, landlords in England, Wales and Scotland must arrange for a Gas Safe registered engineer to carry out an annual gas safety check on every gas appliance and flue in any property they let. You must keep a record of the check, provide a copy to existing tenants within 28 days of the check, and give a copy to any new tenant before they move in. These are legal duties, not best-practice suggestions.

How often you need one

A gas safety check must be carried out at least every 12 months. The check can be done up to two months before the current certificate expires without shortening the next deadline, which gives you a sensible window to get it booked. Missing the annual deadline puts you in breach of the regulations — which is exactly why every landlord we work with is enrolled in our lifetime email and SMS reminder calendar, so the renewal never quietly slips. See gas safety certificates and boiler servicing for how we handle this.

What gets checked

During a CP12 check the engineer inspects each gas appliance for safe operation, checks that gas is burning correctly (using an electronic flue gas analyser to confirm safe combustion), verifies that flues and chimneys are clearing combustion products safely, confirms adequate ventilation, and carries out a gas tightness test to make sure there are no leaks in the pipework. Any defects are recorded, and anything immediately dangerous is dealt with before the engineer leaves.

CP12 vs a boiler service — the difference

This trips a lot of landlords up. A CP12 is a safety check — it confirms appliances are safe to use right now. A boiler service is maintenance — it cleans and checks internal components to keep the boiler running efficiently and protect the manufacturer warranty. They’re different things, but doing both in one visit makes sense: one appointment, one trip, one piece of disruption for your tenant. Our combined service-and-certificate package is built for exactly this.

What happens if you don’t have a valid CP12

The consequences are serious. Letting a property without a valid gas safety record is a criminal offence that can carry unlimited fines and, in the worst cases, imprisonment. Beyond the legal risk, an invalid or missing certificate can affect your landlord insurance and can make it impossible to legally evict a tenant via a Section 21 notice, since the gas safety record must have been provided. And of course, the underlying point is safety: the check exists to catch faults like a cracked heat exchanger leaking carbon monoxide before they harm your tenants.

Carbon monoxide — the real reason it matters

Behind the paperwork is a genuine safety purpose. Faulty gas appliances can leak carbon monoxide, a colourless, odourless gas that kills. An annual check catches the combustion faults and flue problems that produce it, long before a tenant would notice anything wrong. Alongside the CP12, landlords are also required to have a carbon monoxide alarm in any room with a gas appliance — worth checking is in place and working at the same time as the annual gas check.

Making compliance easy

For landlords with one property or a portfolio, the practical goal is never having to think about it. We issue the CP12 as a digital certificate generated on site and emailed instantly to both you and your managing agent the moment the check passes, so the compliance evidence is in your inbox before the engineer leaves the driveway. Combined with automatic annual reminders, that turns a legal obligation that’s easy to forget into something that simply takes care of itself.

The bottom line

A valid CP12 isn’t optional — it’s a legal requirement, a safety safeguard for your tenants, and a protection for you as a landlord. The simplest way to stay on top of it is to book the annual check with a Gas Safe registered engineer who handles the certificate, the reminders and (ideally) the boiler service in one visit. Send your property details through the quote form and we’ll get your gas safety check booked and keep you compliant year after year.