Gas Safety Certificate vs Boiler Service: What's the Difference?
Many London landlords and homeowners confuse a gas safety certificate with a boiler service — they are different in purpose, scope, and legal requirement. This guide explains exactly what each involves, who needs which, and why a combined visit makes economic sense.
What Is a Gas Safety Certificate (CP12)?
A gas safety certificate — formally a Gas Safety Record, often referred to as a CP12 (the form number used on older Gas Safe documentation) — is a legal compliance document confirming that the gas appliances, pipework, and flue arrangements in a property have been inspected by a Gas Safe registered engineer and found to be safe. It is not a maintenance document. It is a point-in-time safety check.
The Gas Safety (Installation and Use) Regulations 1998 require landlords to have all gas appliances in a rented property checked and a gas safety record produced at least once every 12 months. The record must be provided to existing tenants within 28 days of the check, and to new tenants before they move in. Landlords must retain records for at least 2 years.
What the CP12 Check Involves
The Gas Safe engineer inspects all gas appliances in the property — typically the boiler, any gas hob or cooker, and any gas fires or wall heaters. For each appliance, the check covers:
- Visual inspection: Signs of combustion spillage, staining, or physical damage to the appliance and connections
- Flue integrity: Checking the flue is intact, correctly terminated, and shows no signs of spillage or obstruction
- Ventilation: Confirming adequate air supply for combustion (relevant for open-flued appliances)
- Gas tightness: A pressure test of the gas supply pipework to confirm there are no leaks
- Safe operation: The appliance is operated to confirm it ignites, runs, and controls correctly
- Carbon monoxide: CO levels at the flue are checked for appliances that have a flue — levels above the standard trigger immediate action
The result for each appliance is recorded as: satisfactory (safe to use), immediately dangerous (ID — must be disconnected), at risk (AR — should be disconnected as soon as practicable), or not to current standards (NCS — safe but does not meet current standards).
What a Boiler Service Involves
A boiler service is a maintenance visit focused specifically on the boiler — it includes inspection, cleaning, adjustment, and performance testing. A standard service covers:
- Internal boiler inspection — heat exchanger condition, burner, ignition, combustion chamber
- Flue gas analysis — measuring CO/CO₂ ratio and O₂ levels to assess combustion quality
- Burner cleaning and pressure adjustment
- Checking and adjusting expansion vessel pre-charge pressure
- Testing overheat thermostat, pressure relief valve, and ignition
- Checking inhibitor and scale protection levels in the system
- Cleaning condensate trap
A boiler service is about maintaining the boiler in good condition for reliability and efficiency. A gas safety check is about confirming the appliance is safe. The overlap is significant — both involve inspecting the boiler — but the depth differs. A thorough boiler service is a more detailed examination of the boiler than the gas safety check, but the gas safety check covers all gas appliances in the property, not just the boiler.
Who Needs Which
- Landlords: Legally required to have an annual gas safety check (CP12) for all gas appliances in rented properties. A gas safety check is a minimum legal obligation. A boiler service in addition to the CP12 is best practice — it maintains reliability and satisfies warranty conditions, but it is not a statutory requirement for landlords in the same way the CP12 is.
- Homeowners: Not legally required to have either — but strongly recommended to have an annual boiler service to maintain warranty, catch early faults, and maintain efficiency. Many homeowners also choose an annual gas safety check for peace of mind, particularly if they have gas fires or an older installation.
- Tenants: Not responsible for arranging either — these are landlord obligations. However, tenants should check they have received a copy of the current gas safety certificate, and should report any suspected gas appliance faults to their landlord promptly.
Can They Be Done Together?
Yes — a Gas Safe registered engineer can carry out both a boiler service and a gas safety check for all appliances in the same visit. This is common practice and recommended for efficiency. The gas safety check portion covers all gas appliances; the service portion covers the boiler in detail. A combined visit costs less than two separate call-outs.
We offer a combined boiler service and landlord gas safety check in a single visit for London landlords — a more efficient and cost-effective option than booking separately.
Cost Comparison
- Gas safety check only (CP12): £65–£95 depending on the number of appliances and location in London
- Boiler service only: £85–£120
- Combined service and gas safety check: £110–£160 — typically a 15–20% saving versus separate bookings
What Gets Documented
A gas safety check produces the formal Gas Safety Record (CP12 or equivalent) — a legally required document that must be retained. A boiler service typically produces a service record in the boiler logbook and may include a separate report from the engineer. For landlords, both documents are important: the Gas Safety Record for legal compliance, and the service record for warranty compliance and evidence of maintenance should a dispute arise.
Frequency
- Gas safety check (CP12): Mandatory annually for landlords. The check must be within 12 months of the previous one — there is no grace period.
- Boiler service: Annually recommended — and required by most boiler manufacturers to maintain extended warranty. Both the CP12 and service visit are most efficiently arranged together once per year.
Frequently asked questions
Is a gas safety certificate the same as a boiler service?
No — they are different. A gas safety certificate (CP12) is a legal compliance document confirming all gas appliances in the property are safe — it covers all gas appliances and involves a safety inspection. A boiler service is a maintenance visit focused on keeping the boiler in good working condition — it includes cleaning, adjustment, and flue gas analysis. Both involve inspecting the boiler, but a service goes deeper on the boiler while the safety check covers all gas appliances. Landlords legally need an annual CP12; a service is additional best practice.
Do landlords need a boiler service as well as a gas safety check?
Legally, landlords must have an annual gas safety check (CP12). A boiler service is not a statutory requirement for landlords, but most boiler manufacturers require annual servicing to maintain the extended warranty. An unserviced boiler in a rental property that breaks down and requires expensive repair is a foreseeable outcome of poor maintenance — and a landlord who cannot show a service history may face difficulties with warranty claims or with tenants' disrepair claims.
How much does a combined gas safety check and boiler service cost in London?
A combined gas safety check (CP12) and boiler service in London typically costs £110–£160 depending on the number of gas appliances and the borough. This is more economical than booking separately (CP12 £65–£95; service £85–£120 — a combined total of £150–£215 if booked separately). Booking as a combined visit with a single call-out saves both time and money.
How long is a gas safety certificate valid for?
A gas safety certificate (Landlord Gas Safety Record) is valid for 12 months from the date of issue. A new check must be carried out within 12 months of the previous one — there is no grace period. Landlords can arrange the renewal up to 2 months before expiry and still retain the original anniversary date for future renewals.