Gas Safety Certificate (CP12) Explained

If you're a landlord, letting agent, or you've just been asked for your "CP12" and had no idea what that meant, you're not alone. It's one of those terms that gets thrown around constantly in the rental world but rarely explained properly. Here's what a gas safety certificate actually is, why it matters, and what to do about it.

What is a CP12, exactly

A CP12, more correctly called a Gas Safety Record, is the certificate a Gas Safe registered engineer issues after checking all the gas appliances, flues and pipework in a property. It confirms everything is working safely, or flags anything that isn't.

The name "CP12" comes from an old industry code and has stuck around even though the official term has changed. You'll still hear both used interchangeably by landlords, agents and engineers.

The check covers things like:

• Boiler and any other gas appliances (cookers, fires, heaters)
• Gas pipework and connections
• Flue and ventilation, checking for safe removal of fumes
• Correct operating pressure and gas flow
• Signs of wear, corrosion or unsafe installation

Who legally needs one

If you're a private landlord in England or Wales, you're legally required to have a valid gas safety check carried out every 12 months on every gas appliance and flue in the property, and to give tenants a copy of the certificate. This is set out clearly on GOV.UK and enforced through your local council.

Homeowners aren't legally required to get one, but it's still sensible to have your gas appliances checked regularly, particularly if you're relying on an older boiler. If you're wondering whether a check-up is even worth it, our guide on how often a boiler should be serviced covers the reasoning.

Letting agents managing properties on a landlord's behalf usually arrange the CP12 too, so if you're a tenant and haven't seen one, it's worth asking.

What happens during the check

An engineer will inspect each appliance, test for leaks, check ventilation, and confirm the flue is clearing fumes properly. Most checks take between 30 and 60 minutes per property, depending on how many appliances there are.

If something's unsafe, the engineer has a legal duty to act, which can mean disconnecting the appliance until it's fixed. This is one reason a CP12 is worth getting done properly rather than rushed. Only use engineers listed on the Gas Safe Register, it's the only official register of engineers legally allowed to work on gas in the UK.

How much does a CP12 cost

Prices vary depending on the number of appliances and location, but a typical certificate for a single boiler in a Midlands rental property usually falls somewhere in the £60 to £120 range. Multiple appliances or larger properties push that higher.

If your check throws up a fault, that's a separate repair cost. Persistent issues like banging noises or a boiler that keeps losing pressure are often picked up during these checks and worth sorting before they become bigger problems.

When it's time to think about a new boiler

Sometimes a gas safety check reveals that a boiler is genuinely past its best rather than just needing a minor repair. If you're seeing repeated faults, our guide to signs you need a new boiler is a good next read. National providers often quote £3,000 or more for a straightforward combi swap, but it's worth comparing that against a fixed, transparent price. Independent research from Which? can help you understand what different brands and models offer before you commit.

If a replacement does turn out to be the right call, our new boiler cost guide breaks down realistic pricing, and boiler finance is worth a look if you'd rather spread the cost.

Getting your CP12 sorted

Whether you're a landlord due your annual check or a homeowner wanting peace of mind, book with a Gas Safe registered engineer who covers your area. We arrange gas safety checks, servicing and boiler replacements across the Midlands, see our coverage areas to check we're near you, or get a fixed price if you already know you need a new boiler.