Of all the compliance documents a UK landlord has to keep on top of, the CP12 is the one most likely to be looked at by an insurance assessor, a letting agent, or, worst case, the Health & Safety Executive. It’s a one-page certificate that proves your tenanted property has been inspected for gas safety in the last 12 months by a Gas Safe registered engineer. The principle is simple. The practice — particularly for landlords running multiple properties or HMOs — is where it gets fiddly.
1. What the CP12 actually covers
A CP12 is the output of a defined inspection of every gas appliance, the flue serving it, the gas pipework, and the gas meter. The engineer checks each of:
- Appliance condition — physical state, manufacturer requirements, no obvious damage
- Operating pressure — gas valve outlet pressure within manufacturer spec
- Combustion — flue gas analyser reading (CO/CO&sub2; ratio)
- Flue integrity — secure, sealed, products of combustion going where they should
- Ventilation — adequate fresh-air provision for room-sealed and open-flue appliances
- Gas tightness test — pressure-drop test on the pipework
- Carbon-monoxide alarm — presence and operation (mandatory in England since 2022)
Each appliance gets a separate line on the certificate. Any defect is classified “At Risk”, “Immediately Dangerous”, or “Not to Current Standards” with a code (ID, AR, NCS) and a written description.
2. The legal framework
The Gas Safety (Installation and Use) Regulations 1998 are the statute. The key duties for a landlord (regulation 36):
- Ensure every gas appliance, flue and pipework you provide is checked annually for safety
- Maintain records of each check for at least 2 years
- Provide the tenant with a copy of the current CP12 within 28 days of inspection (or before they move in for new tenancies)
- Ensure all work is carried out by a Gas Safe registered engineer
The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 added a carbon-monoxide alarm requirement in any room with a fixed combustion appliance in England (excluding gas cookers, but including everything else). The CP12 process now includes verifying the CO alarm.
3. What it costs in Kent in 2026
Domestic single-appliance CP12 in our Kent coverage area:
- Combi boiler only, no service: £85
- Combi + 1 additional appliance (cooker / fire): £95–£110
- System or regular boiler + cylinder + cooker: £110–£130
- CP12 combined with annual service (recommended): usually £110–£140 total — cheaper than booking separately
- HMO (3+ appliances, multiple flats): from £120 plus £30/appliance over 3
4. Combining CP12 with the annual service
A CP12 is a safety inspection, not a service. Modern manufacturer warranties (Worcester, Vaillant) usually require an annual manufacturer-spec service to keep the warranty alive. Combining the two in one visit:
- Saves you a second £25–£40 call-out
- Keeps the manufacturer warranty intact
- Catches developing issues (sludge, low pressure trend, pump noise) before they become emergencies
- Documents both events on the engineer’s job-sheet, useful if a defect ever needs proving
5. How to schedule across a portfolio
Portfolio landlords with 5+ properties usually fall into one of three scheduling patterns:
- Anniversary-based: each property renewed by its own anniversary date. Spreads cost through the year.
- Quarterly batches: group properties by month and renew in clusters. Cheaper per-visit if engineer travel is reduced.
- Letting-agent managed: agent flags 60 days before expiry and books engineer; landlord pays direct.
For Kent landlords with multiple properties we offer a managed CP12 schedule — we hold the renewal dates, contact tenants for access, and bill quarterly. No more “oh no, my landlord cert expired three weeks ago” emails.
6. The renewal window — why it matters
If you renew the CP12 within 10–12 months of the previous inspection, the new certificate runs from the previous expiry — not the new inspection date. So if your old cert expires 1 October and you re-inspect on 15 September, the new cert runs to 1 October next year, not 15 September. Doing the inspection early doesn’t cost you anything; doing it late does.
7. What about all-electric properties?
No gas, no CP12. But you do still need:
- EICR (Electrical Installation Condition Report) — mandatory for all rented properties in England, renewed every 5 years
- Smoke alarms — one on each storey
- CO alarm — if there’s a wood-burning stove or other solid-fuel combustion appliance
- PAT testing — for any portable appliances the landlord provides
8. Tenant access — the awkward bit
Tenants legally have to allow reasonable access. In practice some don’t. The HSE accepts you can’t force entry, but you must document attempts. The pattern that holds up under scrutiny:
- First letter or email — 14 days’ notice of the inspection window
- Second letter if no response — reminder, plus copy to letting agent if applicable
- Third attempt with a different proposed time
- If still refused, write to the tenant explaining the legal duty and consequences for their safety
Keep copies of all communication. If an HSE investigation ever happens, the paper trail is what matters — not the absence of the inspection itself.
9. Use Gas Safe, not “CORGI”
Gas Safe Register replaced CORGI in 2009. If a contractor still advertises “CORGI registered” on their van, that’s an old van or a contractor who hasn’t stayed current. Every Gas Safe engineer carries a photo ID card showing their unique ID number and the categories they’re qualified for. The CP12 is invalid without it.
South East HVAC handles annual CP12 inspections across our Kent coverage area, including portfolio scheduling for letting agents and landlords managing more than a handful of properties.