What is a CP12 gas safety certificate
If you let out a property with any gas appliance in it, you need a valid gas safety record. Everyone calls it a CP12. The name comes from an old British Gas form number and it stuck.
The certificate is proof that a Gas Safe registered engineer has inspected every gas appliance, pipe and flue in the property and confirmed they are safe to use. Without a current one you are breaking the law, and you are letting people sleep in a building where nobody has checked the boiler.
This guide covers what the check involves, how often you need it, what happens when something fails, and what it costs in London.
Who needs a CP12
You need an annual gas safety check if you rent out property in England, Scotland or Wales and that property contains gas appliances, gas pipework or a flue that you own.
That includes landlords of houses and flats, letting agents acting on a landlord’s behalf, housing associations, and anyone letting a room in a property they also live in. It applies to short lets, holiday lets and student housing too.
The duty sits with the person who owns the appliance. If a tenant brings in their own gas cooker, that appliance is theirs. The pipework feeding it and the flue serving it are still yours, so those still get checked.
Homeowners living in their own house do not legally need a CP12. More on that below.
What the law actually says
The Gas Safety (Installation and Use) Regulations 1998 place three main duties on landlords.
- Arrange an annual safety check on every gas appliance and flue by a Gas Safe registered engineer.
- Keep gas appliances, fittings and flues maintained in a safe condition.
- Keep a record of every check and give copies to your tenants.
The Health and Safety Executive enforces these rules. Breaching them is a criminal offence, not a civil one. Fines are unlimited in serious cases and prosecutions do happen, particularly where somebody has been injured. Landlords have gone to prison for it.
There is also a practical consequence. In England, you cannot serve a valid section 21 notice on an assured shorthold tenant if you failed to give them a gas safety record. Miss the paperwork and you may lose the ability to regain possession of your own property.
What the engineer checks
A gas safety check is not the same as a service, and this catches people out. A CP12 confirms the appliance is safe. A service cleans it and keeps it working well. They overlap but they are different jobs.
During a CP12 the engineer inspects the following.
- Gas tightness across the whole installation, testing for leaks at the meter.
- Standing and working gas pressure at each appliance.
- Burner pressure and gas rate against the manufacturer specification.
- The condition of every accessible gas pipe.
- Flues and chimneys, checking that combustion products vent properly to the outside.
- Ventilation, making sure each appliance has enough air to burn safely.
- Safety devices on each appliance, confirming they shut the gas off when they should.
- Combustion performance, usually with a flue gas analyser.
The engineer then writes up each appliance as pass or fail and signs the record. You get the certificate on the day.
If an engineer refuses to look at the flue because the boiler is boxed in with no inspection hatch, you have a problem. Boxed in flues in loft spaces and ceiling voids need access hatches. That is a common reason for a check to be marked incomplete.
How often do you need a CP12
Every 12 months. The certificate does not have a hard expiry date printed on it in the way an MOT does, but the legal duty is annual.
You can carry out the check up to two months before the current record runs out and keep the original renewal date. So if your certificate is dated 14 October, you can have the new check done any time from 14 August onwards and the new certificate still runs to 14 October the following year.
Use that window. It removes the panic of chasing tenant access in the last fortnight, and it stops your renewal date drifting earlier every year.
If you have a portfolio, track expiry dates in a spreadsheet or let your engineer do it. We keep dates for the landlords and managing agents we work with and send reminders before certificates lapse.
What happens if an appliance fails
The engineer classifies the fault and takes action accordingly.
Immediately Dangerous means the appliance presents an immediate risk. With your permission the engineer disconnects it and attaches a warning label. If you refuse permission, the engineer reports it to the gas emergency service.
At Risk means one or more faults could make the appliance dangerous. It gets turned off with your permission and labelled.
Not to Current Standards means the appliance is safe to use but does not meet today’s installation rules. It stays on. The engineer notes it and recommends improvement.
The certificate cannot be issued as a pass while an appliance sits in a dangerous category. Fix the fault, then the engineer signs it off. Small faults get sorted on the same visit. Anything larger gets quoted separately before we touch it.
The paperwork rules landlords forget
Give a copy of the record to your existing tenants within 28 days of the check.
Give a copy to any new tenant before they move in.
Keep the records for at least two years.
For a property let for less than 28 days at a time, display a copy prominently in the property instead.
These deadlines are not suggestions. If you land in a dispute over possession, the dates on the certificate and the date you handed it over are the first things anyone looks at. Send it by email so you have a timestamp.
What does a CP12 cost in London
We charge £120 plus VAT for a domestic gas safety certificate covering the appliances in a standard flat or house.
If you want the boiler serviced at the same time, book both together for £220 plus VAT rather than paying for two separate visits. Most landlords do this because the manufacturer warranty on the boiler needs an annual service anyway. Details on our gas services page and the full price list.
Prices rise for properties with several appliances or for commercial premises, where a commercial Gas Safe engineer is required at £160 per hour plus VAT.
Be careful with quotes well below the market rate. The check takes an engineer the best part of an hour to do properly. Anyone offering to do it in fifteen minutes is not testing the flue.
Do homeowners need a gas safety certificate
No. There is no legal requirement if you own and live in your home.
Getting one anyway makes sense. Faulty appliances leak carbon monoxide, which you cannot see, smell or taste. Gas Safe Register data shows that a large number of UK homes contain at least one unsafe gas appliance and most owners have no idea.
It also helps when you sell. A buyer’s solicitor asking about the boiler is easier to answer with a certificate than with an opinion.
Fit an audible carbon monoxide alarm near every gas appliance regardless. They cost under £30. In England they are now compulsory in rented homes with a fixed combustion appliance.
Frequently asked questions
What does CP12 stand for?
It stands for CORGI Proforma 12, the form number used before Gas Safe replaced CORGI as the UK gas registration body in 2009. The proper name is now a Landlord Gas Safety Record, but almost everyone still says CP12.
How long does a gas safety check take?
Around 45 to 60 minutes for a typical flat with a boiler and a hob. Larger properties with several appliances take longer.
Does the tenant have to be present?
Somebody needs to give access. It does not have to be the tenant. We arrange access directly with residents for the landlords and agents we work with.
What if my tenant refuses access?
Write to them, explain the legal duty and offer several appointment slots. Keep copies of everything. Repeated refusal without a paper trail leaves you exposed, because the duty to check remains yours regardless of the tenant’s behaviour.
Is a CP12 the same as a boiler service?
No. A CP12 confirms appliances are safe. A service cleans and checks the boiler to keep it running well and to satisfy the manufacturer warranty. Book them together and one engineer does both in a single visit.
How do I check my engineer is registered?
Ask for the Gas Safe ID card and check the licence number on the Gas Safe Register website. The card shows which appliance types the engineer is qualified to work on. Every Sandhurst engineer carries one on every job.
