A tenant reports that the boiler seems fine, the hob lights properly, and there are no obvious issues in the property. That can make it tempting to treat the annual gas safety visit as a formality. In practice, a CP12 check is there to confirm that gas appliances and associated flues are safe to use on the day of inspection. If you are asking what does a CP12 check include, the answer goes beyond simply turning appliances on and off.
For landlords, letting agents and property managers, it is a key part of keeping a rental property compliant and reducing avoidable risk. For homeowners, it is also a useful way to understand what a gas safety check covers, particularly if you are arranging one before letting out a property or want reassurance about an appliance.
What does a CP12 check include for landlords?
A CP12 check, often referred to as a landlord gas safety check, is carried out by a Gas Safe registered engineer. The purpose is to inspect the gas appliances that the landlord is responsible for, along with their flues, and confirm whether they are operating safely.
The check usually includes the boiler, gas hob, gas oven, gas fire and any other landlord-owned gas appliance in the property. It also covers the visible flue route where relevant. If there is gas pipework serving those appliances, that will also be considered as part of the safety assessment.
The engineer is not there simply to confirm that an appliance works. A gas appliance can appear to be working normally and still present a safety issue. The check is looking for signs of unsafe combustion, poor ventilation, gas leaks, flue faults and installation issues that could affect safe operation.
If everything is satisfactory, a Gas Safety Record is issued. This is commonly called the CP12 certificate, even though CP12 is an older industry term that is still widely used.
What is actually inspected during the visit?
The exact scope depends on the appliances at the property, how accessible they are and whether there are any immediate concerns. That said, most CP12 checks include a consistent set of safety inspections.
Gas appliances
Each landlord-owned gas appliance is visually inspected and tested as appropriate. The engineer checks whether the appliance is suitable for use, appears correctly installed and is operating safely. That includes looking for obvious damage, signs of wear, missing safety components or evidence that an appliance has been altered incorrectly.
For a boiler, this may include checking the burner operation, case integrity, safety devices and general condition. For a hob or gas fire, it may include checking burner flames, ignition, flame supervision devices and whether the appliance is stable and properly connected.
This is where people often confuse a CP12 check with a full boiler service. They are not the same thing. A gas safety check is focused on safety and basic operation. A boiler service is more thorough and maintenance-led, with cleaning, performance checks and servicing tasks based on the manufacturer’s guidance.
Flues and combustion
Flues are a central part of the inspection because they remove combustion gases from the appliance. If a flue is damaged, disconnected, blocked or poorly installed, dangerous fumes could remain inside the property.
The engineer checks that the flue is fitted correctly, is in an acceptable condition and is terminating properly. They will also look for signs that products of combustion are spilling back into the room instead of being expelled safely. In some cases, this involves carrying out tests around the appliance while it is operating.
Ventilation
Some gas appliances need a suitable air supply in order to burn gas safely. If ventilation openings have been blocked or reduced, the appliance may not receive enough air, which can affect combustion.
As part of the CP12 check, the engineer assesses whether ventilation is adequate for the appliances installed. That may sound minor, but it is a common area where later changes to a property, such as boxed-in areas or covered vents, can create problems.
Gas tightness
A gas tightness test may be carried out to confirm there is no leak on the gas installation. This is one of the most important parts of the visit. Even if there is no smell of gas and no complaint from tenants, a leak can still be present.
If the engineer identifies a leak or suspects an unsafe situation, they will follow the correct safety procedure. What happens next depends on the severity of the issue, but safety comes first.
Operating pressure and burner performance
Where appropriate, the engineer may check that the appliance is receiving the correct gas pressure and that it is burning gas properly. Incorrect pressure or poor combustion can point to appliance faults or installation issues.
These checks are part of establishing whether the appliance is safe in normal use. Again, this is not always the same as carrying out all the steps involved in a detailed annual service.
What information goes on the CP12 certificate?
Once the inspection is complete, the Gas Safety Record sets out the main details of the visit. This normally includes the property address, the inspection date, the appliances checked, the location of each appliance, and whether each item was found to be safe or whether faults were identified.
It also records any safety defects, any action taken, and confirmation of the engineer’s details, registration and signature or equivalent record. If there are defects, the report should make clear what the issue is and whether remedial work is needed.
For landlords, the paperwork matters as much as the inspection itself. Records need to be clear, accurate and easy to provide when required. For letting agents and property managers, organised reporting helps avoid extra chasing and makes it easier to keep compliance records up to date.
What does a CP12 check not include?
This is where expectations need to be realistic. A CP12 check is not a repair visit, and it is not a substitute for proper maintenance.
If a boiler is overdue a service, passing a gas safety check does not mean it is performing efficiently or that it is less likely to break down. Likewise, a CP12 check does not cover general plumbing issues, heating controls unrelated to gas safety, radiator balancing or wider property maintenance items.
It also does not usually cover appliances owned by the tenant rather than the landlord. If a tenant has brought in their own gas cooker, the position can be more complicated, and it is worth checking responsibility clearly rather than making assumptions.
In some properties, access can also affect what is included. If an appliance, meter or flue route cannot be safely accessed, that may limit the inspection and may need to be addressed before the record can be completed properly.
Why the condition of the property matters
A straightforward CP12 check is easier to complete when the property is reasonably accessible and appliances are not boxed in, obstructed or surrounded by stored items. In managed properties, delays often happen because meter cupboards are locked, loft access is not available, or the engineer cannot inspect a flue route properly.
That does not mean every visit turns into a problem. It simply means preparation helps. Clear access, tenant communication and good booking arrangements can make the process much smoother.
For landlords with multiple properties, this is often where using a dependable, office-supported contractor makes a difference. Good communication before and after the visit, practical updates if there is an issue, and a clear report all save time.
What happens if a fault is found?
If an appliance is found to be unsafe, the engineer will classify the issue in line with current gas safety procedures. The outcome depends on the level of risk. In some cases, the appliance may be turned off and labelled accordingly. In others, remedial work can be arranged to put things right.
This is one area where speed and clarity matter. Landlords and agents need to know what has been found, what action is needed and whether the property can continue to be occupied safely. A vague explanation is no use when a tenant is waiting for an update.
Where repairs are needed, it is sensible to deal with them promptly and ensure any follow-up certification is issued once the issue is resolved.
How often should a CP12 check be carried out?
For landlords, the gas safety check must be carried out every 12 months. Leaving it too late creates unnecessary pressure, especially if access is difficult or remedial works are required before the record can be finalised.
Many landlords now arrange the next visit in good time rather than waiting until the last minute. That approach is usually more practical for tenanted properties, particularly where access needs to be coordinated through a letting agent or managing party.
In areas such as Loughborough, Leicester and the surrounding towns, rental properties range from single lets to larger managed portfolios. The more moving parts there are, the more useful it is to have the check booked and documented in an organised way.
A sensible way to look at it
The best way to think about a CP12 check is as a safety inspection with a clear legal and practical purpose. It confirms whether the landlord’s gas appliances and flues are safe at the time of the visit, and it creates a formal record of that inspection.
If you are managing a rental property, it is worth treating the check as part of a wider maintenance plan rather than a once-a-year box to tick. Safe appliances, clear records and prompt follow-up on defects make life easier for everyone involved – landlord, tenant and agent alike.