What Does CP12 Cover for Landlords?

A tenant reports a boiler fault, the letting file is missing paperwork, and the annual inspection date has already passed. That is usually when the question comes up - what does CP12 cover, and what does it not cover?

A CP12 is a Gas Safety Certificate issued after a Gas Safe registered engineer carries out the required checks at a property. For landlords, it is a legal compliance document. For homeowners, it can still be useful as a record of gas safety, but the legal duty sits most clearly with rented properties. The key point is simple: a CP12 covers the safety check of gas appliances, associated flues and relevant gas pipework at the property. It does not replace servicing, repairs or wider heating system maintenance.

What does CP12 cover in practical terms?

A CP12 covers the gas safety inspection of the appliances and installation elements the engineer is instructed to check at the property. In most homes, that means the boiler, gas hob, gas oven, gas fire and any other landlord-supplied gas appliance.

The engineer will inspect each applicable appliance to confirm that it is operating safely. That includes checking for gas tightness, confirming the appliance is set up correctly, assessing ventilation where required, inspecting the flue system, and looking for signs that combustion is unsafe. The aim is not just to see whether the appliance turns on. The aim is to establish whether it presents a risk to occupants.

Where a boiler is included, the flue route matters just as much as the appliance itself. A boiler may appear to run normally while a damaged or poorly terminated flue creates a serious safety issue. That is why the certificate is focused on gas safety rather than simple functionality.

The main items included on a CP12 inspection

Although every property is slightly different, a proper CP12 will usually cover the same core areas.

Gas appliances

Any gas appliance provided by the landlord should be checked. That often includes boilers, cookers, hobs and gas fires. If there is more than one gas appliance in the property, each one should be identified and recorded individually.

The engineer checks that appliances are safe to use, that burner pressure or heat input is satisfactory where relevant, and that safety devices are working correctly. Visual condition also matters. Damage, poor installation, signs of distress or unauthorised alterations can all lead to defects being recorded.

Flues and combustion safety

A CP12 covers the flue connected to each appliance where applicable. The engineer checks that the flue is fitted correctly, in good condition, and discharging combustion products safely.

This is a critical part of the inspection. If fumes are not removed properly, carbon monoxide can build up inside the property. Even where an appliance still runs, unsafe combustion or a defective flue can make it immediately dangerous.

Gas pipework

Relevant visible gas pipework is part of the safety check. The engineer will look for leaks, poor condition, inadequate support, corrosion and other signs of risk. They will also carry out a gas tightness test to confirm the installation is not leaking.

This does not mean every concealed section of pipework is dismantled or exposed. A CP12 is a safety inspection, not a destructive survey. If access is limited, that limitation may need to be recorded.

Ventilation and air supply

Some appliances require permanent ventilation to operate safely. A CP12 includes checks to confirm that required vents are present, unobstructed and suitable.

Blocked vents are a common issue in occupied properties. Tenants may cover openings without realising why they are there. That can directly affect safe combustion, so it forms part of the inspection.

Safety devices and controls

Where relevant, the engineer checks that flame failure devices, case seals and other safety-related features are intact and operating correctly. If an appliance has been altered, poorly maintained or tampered with, it may fail even if it still appears to work.

What information appears on the CP12 certificate?

The certificate is not just proof that someone attended. It records the property address, inspection date, engineer details, Gas Safe registration details, appliance information, the safety checks carried out, and whether any defects were found.

It should also note any remedial action required and whether an appliance has been classified as At Risk or Immediately Dangerous where applicable. That level of detail matters for landlords and managing agents because it creates a documented compliance trail.

For portfolio landlords, housing providers and councils, accurate records are just as important as the inspection itself. A vague or incomplete certificate can create problems later if compliance is questioned.

What a CP12 does not cover

This is where confusion often starts. A CP12 is not the same as a boiler service.

A boiler service is a maintenance procedure designed to keep the appliance efficient, clean and in good working order. It may involve cleaning components, checking condensate arrangements, testing performance in more depth and reviewing wear over time. A CP12, by contrast, is focused on statutory gas safety checks.

There is some overlap, especially when the same engineer carries out both at the same visit, but they are not interchangeable. If a landlord books only a CP12, they should not assume the boiler has been fully serviced unless that work was separately agreed.

A CP12 also does not cover non-gas systems. It does not inspect the electrical installation, water pipework, radiators, general plumbing, or the overall condition of the heating controls unless those points affect gas safety directly. If a property also needs electrical compliance, that would usually fall under an EICR rather than a gas certificate.

Does a CP12 cover tenant-owned appliances?

Usually, no. The landlord's legal duty applies to gas appliances they provide, along with associated flues and installation pipework.

If a tenant brings in their own gas cooker, that appliance is generally not part of the landlord's CP12 responsibility in the same way as landlord-supplied equipment. However, the installation pipework serving it may still be relevant, and there can be practical grey areas in managed properties. That is why clear records about ownership and responsibility matter.

In blocks, HMOs and supported accommodation, the setup can be more complex. Shared plant rooms, communal systems and mixed appliance ownership may change what needs to be inspected and documented.

Does every landlord need a CP12 every year?

For rented properties with gas appliances or gas installation pipework, the annual requirement is well established. The inspection must be carried out by a Gas Safe registered engineer, and the current record must be provided to tenants in line with legal duties.

The timing matters. Leaving it until after the expiry date creates unnecessary risk, especially where access to occupied properties can be difficult. Landlords and agents with multiple properties should treat CP12 planning as a scheduled compliance task rather than a last-minute job.

Why the scope of the inspection matters

Not all visits are booked with the same level of clarity. One client may ask for a certificate for the boiler only. Another may assume the hob and fire are automatically included. If the instruction is unclear, that can affect what is inspected and what appears on the record.

That is why a competent contractor will confirm how many appliances are at the property and what needs to be checked before or at the time of visit. It avoids under-scoping the job and helps ensure the certificate reflects the actual installation.

For landlords, the safest approach is to be explicit. State every gas appliance in the property, confirm whether it is landlord-supplied, and make sure access is available to each one. A missed appliance is not a small admin issue if it later becomes the source of a safety incident.

What happens if faults are found?

If an engineer identifies a defect, the next step depends on how serious it is. Some faults require remedial work before the installation can be regarded as compliant. More serious defects may mean the appliance is classed as unsafe and should not remain in use.

That is another reason to use a properly accredited, fully insured contractor that handles both compliance and remedial work. If issues are found, you need clear advice, correct classification and a practical route to put matters right without delay. For landlords and property managers across London, that operational reliability is often as important as the certificate itself.

If you are asking what does CP12 cover, the short answer is gas safety. The more useful answer is this: it covers the checks that help prove your property's gas appliances, flues and connected installation are safe at the time of inspection. If you treat it as a paperwork exercise, you miss the point. If you treat it as part of a wider safety and maintenance plan, it does its job properly.