A gas safety certificate — formally known as a CP12 or Gas Safety Record — is one of the most fundamental legal requirements for UK landlords. Unlike the EICR which is required every five years, the gas safety check must be carried out every 12 months without exception. Missing the renewal date by even a single day is technically non-compliant.
This guide covers everything landlords need to know about the CP12 in 2026 — what it covers, what happens during the check, how to handle a failed appliance, and how to serve the certificate on your tenants correctly.
What Is a Gas Safety Certificate (CP12)?
A Gas Safety Certificate is a written record produced by a Gas Safe registered engineer after inspecting and testing all gas appliances and pipework in a property. The "CP12" name comes from the checklist format originally used by British Gas — it has become the industry-standard shorthand for any domestic gas safety record.
The certificate confirms that:
- All gas appliances provided by the landlord are operating safely
- Gas pipework is in good condition with no leaks
- Flues and ventilation are adequate for safe operation
- Safety devices (such as thermocouples and automatic cut-offs) are functioning correctly
A CP12 does not cover appliances owned by the tenant. If your tenant has brought their own gas fire or gas-powered appliance, that is their responsibility — though if you have any concerns about it as the landlord, you can raise it with the engineer.
What Does a Gas Safe Engineer Check?
During a gas safety inspection, the Gas Safe registered engineer carries out a series of checks on each appliance and the installation as a whole:
For each appliance:
- Gas tightness (no leaks in the connection or body of the appliance)
- Burner pressure and heat input
- Operation of all safety devices (over-heat cutoffs, thermocouples, flame supervision devices)
- Ventilation — the appliance has adequate air supply
- Flue effectiveness — combustion products are safely vented
For the pipework and installation:
- Gas tightness of the entire installation using a pressure drop test
- Condition of gas meter, regulator, and isolation valve
- Presence and condition of emergency control valve (ECV)
- Any signs of corrosion, damage, or unsuitable fittings
The inspection typically takes 30–60 minutes for a standard 1–2 appliance domestic property. Properties with multiple appliances — a boiler, gas hob, and gas fire — take longer.
Is a Gas Safety Check a Legal Requirement?
Yes, absolutely. The Gas Safety (Installation and Use) Regulations 1998 place a legal duty on landlords to:
- Ensure all gas appliances, pipework, and flues they provide are maintained in a safe condition
- Have an annual gas safety check carried out by a Gas Safe registered engineer
- Keep a record of each gas safety check for at least two years
- Provide a copy of the current Gas Safety Record to new tenants before they move in
- Provide a copy to existing tenants within 28 days of each annual check
Failure to comply is a criminal offence, not a civil matter. Penalties include an unlimited fine and up to six months' imprisonment. In practice, the Health and Safety Executive (HSE) prosecutes landlords who are found non-compliant — and there are several convictions per year.
Beyond criminal liability, a landlord without a valid CP12 cannot serve a valid Section 21 notice to recover possession of the property. This has been confirmed in multiple court cases.
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The gas safety check covers all gas appliances provided by the landlord, including:
- Boilers (combi, system, and conventional heat-only)
- Gas hobs and cookers provided by the landlord
- Gas fires (open-fronted, balanced flue, and gas-effect fires)
- Gas water heaters and back boilers
- Gas radiators on systems provided by the landlord
The check also covers the gas pipework and flues serving those appliances — not just the appliances themselves.
What is not included:
- Appliances owned and brought in by the tenant
- LPG appliances (these are covered by separate regulations, though the same Gas Safe engineers can inspect them)
- Commercial gas appliances (these require a CP42, not CP12)
What the Certificate Looks Like
A Gas Safety Record (CP12) is a standardised document that includes:
- The address of the property
- The date of inspection
- Details of each appliance inspected (type, location, make/model if known)
- Results of each check — pass or fail per item
- Any defects noted and action taken
- An overall result — safe or unsafe for each appliance
- The Gas Safe registration number and signature of the engineer
The certificate is signed by the Gas Safe registered engineer. If an appliance is found unsafe, the engineer must note what action was taken — typically the appliance is isolated (turned off) pending repair or replacement.
What Happens If an Appliance Fails?
If the engineer finds an appliance to be unsafe, they have a duty to make it safe. This typically means isolating the appliance — turning off the gas supply to that specific appliance and, where necessary, labelling it as unsafe to use.
There are three formal categories under the Gas Industry Unsafe Situations Procedure:
Immediately Dangerous (ID): The appliance presents an immediate risk of injury. The engineer will turn it off and disconnect it, and may cap the supply. The appliance must not be used until repaired or replaced by a competent engineer.
At Risk (AR): The appliance is not immediately dangerous but could become so. The engineer will advise the landlord of the required action and a timescale. If the landlord cannot be contacted or refuses to act, the engineer is required to make the appliance safe.
Not to Current Standard (NCS): The appliance does not meet current requirements but is not immediately dangerous. This is noted on the certificate and an improvement is recommended.
As the landlord, you are responsible for arranging repairs or replacement promptly. An appliance that is isolated cannot be used — for a boiler, this means no heating or hot water — so acting quickly protects both your tenants and your legal position.
Providing the Certificate to Tenants
The Gas Safety Regulations prescribe exactly when you must hand over the certificate:
- New tenants: A copy must be provided before the tenancy starts. If the gas safety check is being carried out on the day of move-in, you must provide it on that day. You cannot wait until after the tenancy has begun.
- Existing tenants: A copy of the annual renewal must be provided within 28 days of the inspection being carried out.
- All tenants: If a tenant requests a copy of the previous two years' records, you must provide them within 28 days.
You can provide the certificate as a physical copy or by email — the regulations do not require paper, but you need to be able to evidence that the tenant has received it. Sending by email with read receipt or by post with proof of delivery is the safest approach.
Fines for Not Having a Valid CP12
The financial and legal consequences of non-compliance are severe:
- Criminal prosecution by the Health and Safety Executive (HSE)
- Unlimited fine (there is no statutory maximum)
- Up to six months' imprisonment in serious cases
- Civil liability if a tenant or third party is injured as a result of a gas-related incident in your property
- Section 21 rendered invalid — you cannot recover possession using Section 21 without a valid CP12
The HSE publishes prosecutions on its website. Landlords have been prosecuted for having no gas safety certificate, for using unregistered engineers, and for failing to maintain appliances that subsequently caused carbon monoxide incidents.
Carbon monoxide (CO) is produced by poorly serviced gas appliances. It is colourless, odourless, and kills. This is not a paperwork requirement — it is a life safety issue.
CP12 vs CP42: What Is the Difference?
CP12 is the Gas Safety Record for domestic residential properties — houses, flats, and HMOs used as dwellings.
CP42 is the equivalent certificate for commercial properties — offices, restaurants, shops, hotels, and any property used for commercial purposes rather than as a dwelling.
If you are a landlord of:
- Residential rental property → you need a CP12 (domestic gas safety certificate)
- Commercial premises → you need a CP42 (commercial gas safety certificate)
Some properties mix residential and commercial use — for example, a flat above a commercial kitchen, or a HMO in a building that also contains a business. In these cases, you may need both.
How Much Does a Gas Safety Certificate Cost in London?
At My Landlord Certificate, gas safety certificate pricing is:
| Appliances | Price | |---|---| | 1 gas appliance | £49.99 | | 2 gas appliances | £59.99 | | 3 gas appliances | £69.99 | | Gas Safety + Boiler Service | £84.99 |
Prices include VAT. Additional charges: Congestion Zone supplement (£20 for central London properties) and parking (£10 if no free parking available).
The certificate is emailed to you within 24 hours of the inspection. All our engineers are Gas Safe registered — you can verify any engineer's registration at the Gas Safe Register before or after the visit.
Keeping Track of Renewals
Because a CP12 is valid for exactly 12 months, staying on top of renewal dates is critical for landlords with multiple properties. We recommend:
- Adding the renewal due date to your calendar the day you receive each certificate
- Using a landlord compliance spreadsheet to track all properties
- Booking the renewal 6–8 weeks before the anniversary date — this gives time to reschedule if needed without going out of date
You can book your annual gas safety certificate online with next-day appointments across all 33 London boroughs.
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