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Gas Safety (CP12): what it proves and what it doesn't

The CP12 is the landlord gas certificate most people know — and most commonly misunderstand. What it proves, what it doesn't, and the traps.

The CP12 — the Landlord Gas Safety Record — is the certificate most landlords are familiar with, and also the one most commonly misunderstood. Here’s what it does, what it doesn’t, and the traps.

What the law actually says

Under the Gas Safety (Installation and Use) Regulations 1998, if you let a property with any gas appliance, pipework or flue that’s the landlord’s responsibility, you must:

  1. Have a gas safety check carried out every 12 months by a Gas Safe registered engineer.
  2. Give the tenant a copy of the record within 28 days of the check (or before they move in).
  3. Keep the record for at least two years.
  4. Maintain the gas pipework, appliances and flues in a safe condition.

What the certificate proves

That on the day of the check, each tested appliance met the safety standards in place at the time. That’s it. A CP12 is a snapshot, not a warranty. An appliance can pass its check in January and develop a fault in March.

What it doesn’t prove

  • It doesn’t prove the appliance is serviced to the manufacturer’s standard. A gas safety check and a service are different jobs. Some engineers bundle them; most don’t. If the boiler manual says annual service, the CP12 alone doesn’t discharge that.
  • It doesn’t cover tenant-owned appliances (e.g. a tenant’s own gas cooker). You’re still responsible for the connection point.
  • It doesn’t cover LPG bottles the tenant brings into the property, but it does cover any fixed LPG installation.

The 10–12 month window

You can carry out the check up to two months before the old one expires without losing any of the 12-month period — the new expiry runs from the old one, not the check date. This is the “10–12 month rule” and it’s the single most useful thing to know about CP12 logistics. Lose track of this and your expiry dates creep forward every year.

What makes a certificate invalid

Engineer not on the Gas Safe register on the day of the check. Appliance missed off the record. Serial numbers or addresses wrong. If challenged, these are the points a lawyer will go to first.

Access problems

If a tenant refuses entry, you still need to demonstrate you took reasonable steps. Keep a paper trail: texts, emails, letters with dates. Courts and councils will ask for it.

Penalties

A breach is a criminal offence. Fines are unlimited in theory, though most prosecutions end up in the £500–£5,000 range depending on severity. More practically: without a valid CP12, you historically couldn’t serve a valid Section 21 notice — and while Section 21 itself is being abolished in May 2026, the gas safety obligation doesn’t change.

References and further reading

General guidance, not legal advice. If in doubt about a specific property, speak to a Gas Safe registered engineer or a qualified lawyer.