CP12 Certificate Guide | West and North West London

A landlord gas safety certificate, officially the Landlord Gas Safety Record (LGSR), but commonly called a CP12 certificate, records the annual safety checks on the gas appliances and flues a landlord provides. The checks must be completed every 12 months by a Gas Safe registered engineer. Existing tenants must receive the record within 28 days, new tenants before moving in, and landlords must keep each record for two years. Installation pipework has a separate maintenance duty and is not formally part of the CP12 check. The Happy Heating Co goes beyond that minimum. On every gas-related attendance, we gas-tightness-test the complete installation as our own safety standard. We are Gas Safe registered (657972) and issue digital CP12 records across West and North West London through our landlord gas safety certificate service.

If you let a property with gas in it, the annual gas safety check is a legal duty. This guide explains what a CP12 covers, the deadlines that matter, how the 2026 tenancy changes affect landlords and what to expect when arranging a local check.

Key takeaways

A CP12 and a boiler service are separate jobs, although both can be completed during one appointment.
You can renew up to two months early without losing the original renewal date.
The annual check covers relevant landlord-provided gas appliances and flues. Installation pipework has a separate maintenance duty.
Since 1 May 2026, most private tenancies in England are assured periodic tenancies and Section 21 has been abolished. The annual gas-safety duties remain in force.
Although it is not part of the statutory CP12 minimum, we gas-tightness-test the complete installation on every gas-related attendance as our own safety standard.

What is a CP12 / landlord gas safety certificate?

“CP12” is the old CORGI form number for what’s now called the Landlord Gas Safety Record (LGSR). The name stuck. Landlords, letting agents and engineers still say CP12 certificate, and it means the same thing. The record is what a Gas Safe registered engineer issues after carrying out the annual gas safety check the law requires on rented homes.

The record confirms that each gas appliance the landlord provides, the boiler, gas hob or gas fire, and its flue has received the required safety checks. It lists what was checked, any defects found, what action was taken and whether each appliance was safe to use. Your tenant gets a copy. You keep one for your records.

Installation pipework is different. HSE says it is not formally covered by the annual gas safety check, although landlords must maintain it safely and HSE recommends asking the engineer to test the whole gas system for soundness and visually examine accessible pipework. Although that complete-installation test is not the statutory CP12 minimum, we carry it out on every gas-related attendance because the safety of our work and the customer’s gas installation matters.

Who needs a landlord gas safety certificate?

You need one if you let a property containing gas appliances and flues that you, as landlord, provide for the tenant. That covers the great majority of private lets we look after across Queen’s Park, Kilburn and Maida Vale, flats, terraces and HMOs alike:

Privately rented houses and flats, including most assured periodic tenancies in England.
Rooms let in shared houses and HMOs.
Short-term and holiday lets.
Properties managed by a letting agent on your behalf. The duty can be delegated to the agent in writing, but the check still has to happen.

One carve-out. If an appliance belongs to the tenant, their own gas cooker, for example, the tenant is responsible for that appliance and any flue serving only that appliance. You remain responsible for maintaining the associated installation pipework safely.

How often do you need a CP12?

Every 12 months. The law requires an annual gas safety check on all relevant appliances and flues, carried out by a Gas Safe registered engineer. No exceptions for newer boilers or recently checked properties.

There’s one helpful flexibility, introduced in April 2018. You can have the check done up to two months early and keep your original renewal date. It works like an MOT. Renewing ahead of the deadline doesn’t reset the clock against you. In practice, that means you can book the next CP12 certificate comfortably before the current one expires and never risk a gap in cover, even across tenancy changes.

What does a gas safety check involve?

A Gas Safe registered engineer inspects each appliance and flue to confirm it’s operating safely. On a typical visit that means checking:

The appliance is burning correctly, right gas pressure, clean combustion.
The flue or chimney is carrying combustion products safely outside.
There’s adequate ventilation around the appliance.
Safety devices cut in as they should.
As our standard practice, we carry out a gas-tightness test on the complete gas installation.

If something fails, it goes on the record with advice on the fix. Where there’s an immediate danger, the engineer may disconnect the appliance (with permission) to keep everyone safe. HSE says the record should still be issued when the checks finish. It records the results rather than acting as a simple pass certificate and should not be delayed until remedial work is complete. Keep any follow-up repair records with it. Repairs are separate work. We handle those under boiler repairs.

CP12 certificate vs a boiler service, what’s the difference?

The question landlords ask us most, and the distinction matters. A CP12 certificate is a safety check, a boiler service is maintenance. One keeps you legal. The other keeps the boiler reliable. They’re not interchangeable.

Purpose