Understanding Gas Safety Certificates: A Complete Guide
Everything landlords and homeowners need to know about CP12 gas safety certificates: legal requirements, what is checked, and how to book.
By First Certify · 2025-06-15 · 7 min read
First Certify is a UK property compliance platform staffed by accredited assessors and qualified engineers. This article has been reviewed for accuracy against current UK regulations, including MEES, the Electrical Safety Standards 2020, and the Gas Safety (Installation and Use) Regulations 1998.
A Gas Safety Certificate, commonly known as a CP12, is a document that confirms all gas appliances, pipework, and flues in a property have been safety checked by a Gas Safe registered engineer. For landlords, it is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998.
The check must be carried out every 12 months. Only engineers on the Gas Safe Register are legally permitted to carry out the inspection and issue a CP12. The engineer inspects all gas appliances in the property, including the boiler, gas hob, gas fire, water heater, and any other gas fuelled equipment.
During the check, the engineer tests for safe operation, adequate ventilation, and clear flues. They carry out a gas tightness test on the installation pipework to check for leaks. They also check that safety devices are functioning correctly and that appliances are burning gas efficiently.
The CP12 certificate must be given to tenants within 28 days of the check. For new tenants, a copy must be provided before they move in. Landlords must retain records for a minimum of two years.
Failing to have a valid gas safety certificate is a criminal offence. Penalties can include unlimited fines and, in serious cases, imprisonment. More importantly, a faulty gas appliance can produce carbon monoxide, which is odourless, colourless, and potentially fatal.
The check itself takes 30 to 45 minutes for a standard property with a boiler and a couple of appliances. The engineer will need access to all gas appliances and the meter. Appliances will be turned on and off during testing, so it is best to coordinate with tenants to ensure access.
At First Certify, our engineers are Gas Safe registered and experienced in working around occupied properties. We issue the CP12 certificate within 72 working hours of the visit — most within 24 to 48. You can book online in minutes, and if you need an EPC or EICR at the same time, we can combine them in a single visit.
FAQs
How often do I need a gas safety certificate?
Landlords must have a gas safety check carried out every 12 months by a Gas Safe registered engineer. The certificate must be given to tenants within 28 days, and to new tenants before they move in.
Who can carry out a gas safety check?
Only engineers on the Gas Safe Register are legally permitted to carry out gas safety checks and issue CP12 certificates. Always ask to see the engineers Gas Safe ID card before allowing them to work on your property.
What happens if I do not have a valid gas safety certificate?
Failing to have a valid CP12 is a criminal offence under the Gas Safety (Installation and Use) Regulations 1998. Penalties can include unlimited fines and, in serious cases, imprisonment.