What Is a Gas Safety Certificate?
A gas safety certificate — officially known as a CP12 — is a document issued by a Gas Safe registered engineer after inspecting all gas appliances, pipework, and flues in a property. It confirms that the gas installations are safe to use and meet current regulations.
For landlords in England and Wales, having a valid gas safety certificate is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998. It's not optional, and the consequences of non-compliance are severe.
Who Needs a Gas Safety Certificate?
Every landlord in the UK who rents out a property with gas appliances or gas pipework must have an annual gas safety check carried out by a Gas Safe registered engineer. This applies to:
- Private landlords (individual buy-to-let investors)
- Housing associations and registered social landlords
- Property management companies acting on behalf of landlords
- Airbnb and short-term let hosts (yes, this includes you!)
- Commercial landlords with gas installations
The only exception is if the property has no gas supply or gas appliances whatsoever — but even then, if there's capped-off gas pipework, an engineer should verify it's safe.
What Does the Gas Safety Check Cover?
During a CP12 inspection, the Gas Safe registered engineer will check:
- All gas appliances: Boilers, gas cookers, gas fires, gas water heaters — every gas appliance in the property.
- Gas pipework: Visible gas pipes are checked for leaks, damage, and correct routing.
- Flues and ventilation: All flues are tested to ensure combustion products vent safely to the outside. Ventilation is checked to confirm adequate air supply for combustion.
- Safety devices: Flame failure devices, thermocouples, and other safety mechanisms are tested.
- Gas pressure and tightness: The gas supply is tested for correct pressure and any leaks.
- Combustion analysis: The engineer measures the combustion gases (CO₂, CO, O₂) to ensure complete and safe burning.
Your Legal Obligations as a Landlord
Annual Inspection
You must arrange a gas safety check every 12 months. The certificate is valid for one year from the date of inspection. You can arrange the check up to 2 months before the current certificate expires without losing any validity — the new certificate will be dated from the expiry of the existing one, not the date of the check.
Provide a Copy to Tenants
You must give a copy of the current gas safety certificate to:
- Existing tenants within 28 days of the check being completed.
- New tenants before they move in.
Many landlords and agents now provide digital copies via email, which is perfectly acceptable.
Keep Records
You must retain copies of gas safety certificates for at least 2 years. We recommend keeping them indefinitely as part of your property compliance records.
Use a Gas Safe Registered Engineer
The inspection must be carried out by an engineer who is on the Gas Safe Register. You can verify any engineer's registration at GasSafeRegister.co.uk using their ID number. Heat-Plex's Gas Safe registration number is 578913.
What Happens If You Don't Comply?
The Health and Safety Executive (HSE) takes gas safety seriously. Penalties for non-compliance include:
- Criminal prosecution: Landlords can be charged with a criminal offence.
- Fines: Unlimited fines for the most serious offences.
- Imprisonment: Up to 6 months in prison (or up to 2 years for more serious offences under the Corporate Manslaughter Act if a death results).
- Civil liability: If a tenant is harmed by a gas-related incident and you don't have a valid certificate, you'll face civil claims for damages.
- Insurance invalidation: Most landlord insurance policies require a valid CP12. Without one, your policy may be void.
- Section 21 restrictions: In England, you cannot serve a valid Section 21 eviction notice (no-fault eviction) without a current gas safety certificate.
How Much Does a Gas Safety Certificate Cost in London?
Prices vary, but typical costs in London are:
- 1 appliance (e.g., boiler only): £65–£85
- 2 appliances (e.g., boiler + gas cooker): £80–£100
- 3+ appliances: £90–£120
At Heat-Plex, our CP12 certificates start from £65, with same-day availability and digital certificate delivery. We also offer multi-property discounts for landlords with portfolios.
CP12 vs. Boiler Service: What's the Difference?
This is one of the most common questions we receive from landlords, and the distinction matters:
- A gas safety check (CP12) is a safety inspection. It confirms that the gas appliances are safe to use, the flues are clear, and there are no gas leaks. It fulfils your legal obligation.
- A boiler service is a maintenance procedure. It includes cleaning internal components, checking efficiency, and identifying developing faults. It keeps the boiler running well and maintains manufacturer warranties.
The two are often confused because they overlap, but they're not the same thing. We recommend doing both simultaneously — our landlord care plans bundle the annual CP12 and boiler service together for a single monthly fee, saving time and money.
Tips for Managing Gas Safety Across Multiple Properties
- Set up a tracking system: Maintain a spreadsheet or use property management software to track certificate expiry dates for each property.
- Book renewals 2 months early: This gives you flexibility and means you don't lose any validity if the check happens before the old one expires.
- Coordinate with tenants in advance: Give tenants plenty of notice (we recommend at least 2 weeks) and offer morning and afternoon slots.
- Use one provider for all properties: Working with a single trusted engineer or company means consistent quality, bulk discounts, and a single point of contact. At Heat-Plex, we manage gas safety for landlords with single properties through to portfolios of 50+.
- Consider a landlord care plan: Our plans include annual CP12 certificates, boiler servicing, priority repairs, and no call-out fees. We handle the scheduling, tenant liaison, and record-keeping for you.
What If the Engineer Finds a Problem?
If the gas safety check reveals a fault, the engineer will classify it as one of the following:
- Immediately Dangerous (ID): The appliance poses an immediate risk and must be disconnected or made safe on the spot. The gas supply to the appliance will be turned off and labelled. It cannot be used until repaired.
- At Risk (AR): The appliance is not immediately dangerous but could become so. The engineer will recommend repair and may disconnect it with the tenant's agreement.
- Not to Current Standards (NCS): The installation doesn't meet current standards but isn't unsafe. The engineer will note it and recommend upgrading.
As the landlord, it's your responsibility to arrange repairs promptly. Continuing to let a property with a known gas safety issue is a serious offence.
Book Your Gas Safety Inspection
Don't leave gas safety to the last minute. At Heat-Plex, we provide efficient, reliable gas safety inspections for London landlords with same-day certificate delivery. Whether you have one property or fifty, our landlord services team makes compliance easy.
Book online or call 020 7622 0444. Ask about our multi-property discounts and landlord care plans.