Gas Safety Certificates for Landlords: Complete Guide 2025

If you rent out a property in London that has gas appliances, an annual gas safety certificate — formally called a gas safety record, but widely known as a CP12 — is not optional. It is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998, and failing to comply can result in prosecution, significant fines and, in the worst cases, imprisonment.

What is a gas safety certificate?

A gas safety certificate is the written record produced by a Gas Safe registered engineer after inspecting all gas appliances, pipework, flues and ventilation in a rental property. The engineer checks that everything is operating safely, identifies any faults, and issues the certificate confirming the result of the inspection. The document is formally called a gas safety record — CP12 is trade shorthand that has stuck.

What does the law require?

Under Regulation 36 of the Gas Safety (Installation and Use) Regulations 1998, landlords must:

• Arrange an inspection of all gas appliances and flues by a Gas Safe registered engineer at least once every 12 months
• Provide a copy of the certificate to existing tenants within 28 days of the inspection
• Give new tenants a copy before they move in
• Retain records for a minimum of 2 years

The duty rests with the landlord, even where a letting agent manages the property day to day. However, landlords can contractually delegate the obligation to their agent.

What does a gas safety inspection cover?

The inspection covers every gas appliance in the property — typically the boiler, gas hob, gas oven and any gas fire. The engineer checks:

• Safe operation of each appliance
• Gas pressure and supply condition
• Flue and ventilation adequacy
• Emergency control valve condition
• Pipework and connections

If a fault is identified, the engineer may mark the appliance as At Risk or Immediately Dangerous and advise on or carry out remedial work.

How much does a gas safety certificate cost in London?

For a standard one-bed or two-bed London flat with a combi boiler and no additional gas appliances, expect to pay in the region of £80–£120 for the inspection and certificate alone. Combining the gas safety check with an annual boiler service — which is good practice — typically costs around £150–£200. Always confirm what is included before booking.

What are the penalties for not having a certificate?

A landlord who fails to comply with the gas safety regulations can be prosecuted under the Health and Safety at Work Act 1974. The penalties include an unlimited fine and up to two years in prison. Beyond the legal risk, failure to hold a valid certificate can also invalidate buildings and contents insurance and prevent a landlord from serving a valid Section 21 notice.

When should you book?

The certificate is valid for 12 months from the date of inspection. Most landlords book 2–4 weeks before the expiry date to avoid a lapse. If you are unsure when your current certificate expires, check the top of the document — the inspection date and next due date are stated on the record.