Landlord Gas Safety Certificate (CP12): Rules, Cost and What Is Checked

What Is a CP12 Certificate and Where Does the Name Come From?

A landlord gas safety certificate is the document a Gas Safe registered engineer produces after inspecting all gas appliances, flues and pipework in a rented property. The formal name under the Gas Safety (Installation and Use) Regulations 1998 is a Landlord Gas Safety Record (LGSR), but practically everyone in the industry — landlords, letting agents and solicitors alike — still calls it a CP12.

The name CP12 is a hangover from the era when CORGI (the Council for Registered Gas Installers) regulated gas engineers in the UK. CP12 stood for "Corgi Proforma 12" — the specific form used to record the inspection. CORGI was replaced by the Gas Safe Register in April 2009, but the nickname stuck. You will still see CP12 referenced on compliance checklists, landlord insurance policies and property management software, so it is worth knowing both names.

The certificate itself is not just a formality. It is a legal record that confirms each appliance was safe at the time of inspection. If anything goes wrong later — a carbon monoxide incident, a gas fire, a disrepair claim — the certificate is your primary evidence that you met your duty of care.

Who Needs a Landlord Gas Safety Certificate? Legal Scope

The requirement comes from the Gas Safety (Installation and Use) Regulations 1998. They apply to any landlord in England, Scotland or Wales who lets a property containing gas appliances or gas pipework. This includes:

• Private landlords renting houses or flats on assured shorthold tenancies
• Houses in Multiple Occupation (HMOs)
• Housing associations and social landlords
• Letting agents managing properties on a landlord's behalf
• Landlords of commercial premises with gas appliances

The rules apply to both mains natural gas and liquefied petroleum gas (LPG), which is common in rural properties and mobile homes not connected to the gas grid.

One point that trips many landlords up: even if a tenant brings their own gas cooker into the property, you are still responsible for carrying out a CP12 on the landlord-owned pipework and flues. If any gas pipework exists in the property, the obligation applies.

If you have sublet your property to a tenant who is then subletting to a lodger, the original landlord remains responsible for gas safety. You cannot pass this legal obligation on to your tenant, though a written agreement can allocate responsibility clearly if parts of the property are separately managed.

The regulations apply to periodic tenancies, fixed-term tenancies of less than seven years, and licences to occupy. They do not apply to owner-occupied properties — only to rental arrangements.

Key Legal Rules: Timelines and Record-Keeping

The law sets out clear requirements for how often checks must happen and how records must be managed.

• Gas appliances, flues and pipework must be inspected at least once every 12 months by a Gas Safe registered engineer
• Existing tenants must receive a copy of the new certificate within 28 days of the inspection
• New tenants must receive a copy before they move in — not within 28 days, but before the tenancy starts
• Gas Safety Records must be kept for a minimum of two years
• Electronic delivery is permitted as long as the tenant can access the document

There is no grace period once a certificate expires. An expired CP12 — even by a single day — is a breach of the regulations. Landlords can, however, carry out the annual check up to two months early and retain the same renewal date, which is useful for forward planning if you have multiple properties.

The Renters' Rights Act 2025, which received Royal Assent in October 2025, ends Section 21 no-fault evictions in England. It does not relax gas safety obligations in any way. In fact, a valid and uninterrupted chain of CP12 certificates will matter more under the new regime, as landlords pursuing possession under Section 8 will need to demonstrate they have complied with all prescribed information requirements — and a lapsed gas safety certificate weakens that case considerably.

What Is Checked During a CP12 Gas Safety Inspection?

A CP12 inspection covers every gas-burning appliance in the property, along with its associated flue, ventilation and pipework. Here is what a Gas Safe registered engineer will examine:

• Boiler: general condition, installation, correct operation, burner pressure, combustion performance, flue gas analysis where required, and function of safety devices including overheat stats and pressure relief valves
• Gas hob and cooker: condition, correct installation, flame pattern and stability, gas pressure at the burner, and flame failure devices where fitted
• Gas fires and wall heaters: flue spillage test, ventilation adequacy, thermocouple function, and general condition
• Gas water heaters: condition, flue integrity, combustion and safety device checks
• Flues and chimneys: routing, termination point, clearances, integrity of seals, absence of blockages or cracks, and correct draw — a faulty flue is one of the most common causes of carbon monoxide poisoning
• Gas pipework: pressure test for leaks, correct support and routing, condition of joints and valves, and where applicable the condition of any lead or old-style pipework that may need replacing
• Ventilation: each appliance needs an adequate air supply — sealed double-glazing retrofitted in older flats is a frequent cause of insufficient ventilation
• Safety devices: flame failure devices, interlocks, thermocouples, cut-offs and overheat stats are all tested to confirm they operate as designed

A typical inspection takes around 30 minutes for a property with one boiler and one additional appliance. Larger properties or those with multiple gas appliances will take longer.

Following the inspection, each appliance receives one of three outcomes: Safe, At Risk (a defect that needs attention but does not require immediate isolation), or Immediately Dangerous. An immediately dangerous appliance will be disconnected on the spot, and the engineer will advise you in writing of what is needed before it can be returned to service.

What a Valid CP12 Must Contain

Under Regulation 36(3) of the Gas Safety (Installation and Use) Regulations 1998, a valid Landlord Gas Safety Record must include all of the following:

• The date the inspection was carried out
• The address of the property inspected
• The name and address of the landlord or their managing agent
• The name, signature and Gas Safe registration number of the engineer
• A description and location of every appliance or flue inspected
• The results of the inspection for each item
• Details of any defect found, and what action was taken or is required
• Confirmation that the inspection has been completed

If any of these fields is blank or incomplete, the certificate is not valid under the regulations. An incomplete CP12 can be challenged by a tenant, flagged by a local authority housing officer or queried by a buyer's solicitor during a property sale. Always check the document your engineer issues before filing it away.

CP12 Cost: What UK Landlords Typically Pay in 2025/26

The cost of a landlord gas safety certificate varies by region, the number of appliances and engineer availability. For a standard property with one boiler and one additional gas appliance, most UK landlords pay between £60 and £90. At the lower end you will find engineers in the North of England, the Midlands and Scotland; at the upper end, London and the South East.

Prices vary by region — expect the top end (or 20–30% more) in London and the South East, and less in the North and Scotland.

A summer booking will often cost 10–15% less than the same job done in October or November when engineers are busy and some will charge a premium for urgent slots. If you have multiple properties, many engineers offer a reduced per-property rate for a block booking.

Some engineers advertise CP12 checks at £35–£45. Be cautious: at that price point, the inspection is unlikely to be thorough, and an inadequate inspection that misses a real safety issue creates significant liability for the landlord. A certificate that does not stand up to scrutiny after an incident is worse than no certificate at all.

The CP12 price covers the inspection and the certificate. Any remedial work required — replacing a faulty thermocouple, resealing a flue joint, servicing a boiler that is producing unsafe combustion products — is charged separately. Budget for repairs as a separate line.

What Affects the CP12 Price?

Several factors push the cost of a landlord gas safety check up or down:

• Number of appliances: most engineers include one or two appliances in a standard price and charge £10–£35 per additional appliance. A property with a boiler, a gas hob, a gas fire and a separate water heater will cost noticeably more than a flat with just a combi boiler
• Location: London and the South East consistently attract the highest rates. Rural areas can also cost more due to engineer travel time and availability
• Engineer type: a large national gas company will typically charge more than a local sole-trader Gas Safe engineer. Both are legally valid, but the pricing difference can be significant
• Access and timing: easy parking, a ground-floor boiler and a flexible tenant make the job quicker. Awkward access, roof-level flue terminations or an uncooperative tenant can add time
• Combined service packages: many engineers offer a CP12 plus boiler service package at a combined price that is lower than booking each separately. This is usually the best-value approach for landlords, because a serviced boiler is also less likely to produce combustion readings that cause a CP12 to fail
• Urgency: an emergency or same-day slot typically carries a premium of £20–£50 above a pre-booked rate

Prices vary by region — expect the top end (or 20–30% more) in London and the South East, and less in the North and Scotland.

How to Avoid Overpaying: Getting the Best Value CP12

Getting a fair price for your gas safety certificate is straightforward if you follow a few simple steps.

• Always verify the engineer is Gas Safe registered before booking. You can check instantly at the Gas Safe Register website using the engineer's registration number. Only a Gas Safe registered engineer can legally issue a CP12
• Get two or three quotes from local engineers before booking. Use the Gas Safe Register's 'Find an Engineer' tool or reputable comparison sites
• Book in advance and off-peak. A summer booking avoids winter premium pricing and ensures you are not scrambling for an urgent slot when the certificate lapses in November
• Ask about combined packages. A CP12 plus boiler service in a single visit from the same engineer is nearly always better value than two separate bookings, and it is better for the boiler too
• If you have a portfolio of properties, negotiate a block rate. Most sole-trader engineers will agree a reduced per-property price for three or more properties booked together
• Ask for a full written quote before work starts, including what any identified remedial work would cost. This avoids surprises on the day

Red Flags in CP12 Quotes: What to Watch Out For

Not every cheap quote is a bargain, and not every expensive one is legitimate. Watch out for these warning signs:

• No Gas Safe registration number on the quote or invoice. Every legally valid certificate must include the engineer's Gas Safe number — if they cannot provide it upfront, walk away
• Prices below £45 for a single-appliance property. At this level it is unlikely the inspection will be thorough enough to identify real safety issues. If something is later found to have been missed, the landlord — not just the engineer — faces legal exposure
• Pressure to pay cash with no receipt or certificate issued on the day. A valid CP12 must be a written document (paper or electronic) with all required fields completed
• Verbal-only inspections. The check must result in a written Landlord Gas Safety Record — a verbal assurance is worthless legally
• Certificates issued without the engineer visiting the property. This does happen; it is fraud. Tenants or other engineers can notice, and the consequences for the landlord can be severe
• An engineer who cannot explain what they checked or why something passed or failed. A Gas Safe registered engineer should be able to walk you through each appliance's results

Common Reasons a CP12 Fails

Understanding why gas safety checks fail helps you prepare the property and reduce the chance of expensive remedial work.

The single most common failure is combustion outside acceptable limits. This usually means an old or poorly maintained boiler with a tired heat exchanger. The fix is a proper boiler service, sometimes with a part replacement. The root cause is almost always a lack of annual servicing — which is why combining your CP12 with a service makes sense.

Inadequate ventilation is another frequent issue, particularly in older flats where windows have been replaced with sealed double-glazing. Gas appliances need a sufficient air supply to burn safely, and modern draught-proofing can reduce this below safe levels.

Flue problems including cracked seals, soot deposits, blocked terminals or incorrect flue positioning relative to windows and extractor fans are commonly identified. A flue installed too close to an air vent is one of the most common immediately dangerous findings — it creates a direct carbon monoxide risk.

Gas supply leaks are usually caused by a corroded joint, a tired valve or old lead pipework. These are recorded and must be fixed before the certificate can be issued.

Faulty or disconnected safety devices — particularly flame failure devices that have been tampered with or have simply worn out — are classified as immediately dangerous. The appliance will be isolated on the spot.

If an appliance fails, you as the landlord are responsible for arranging repairs with a Gas Safe registered engineer before the property can legally be rented with that appliance in service. Do not attempt to reconnect or repair gas components yourself.

Penalties for Non-Compliance

Failing to hold a valid landlord gas safety certificate is a criminal offence under the Gas Safety (Installation and Use) Regulations 1998, prosecuted under the Health and Safety at Work etc. Act 1974.

The penalties on conviction can include:

• Fines of up to £6,000 per offence — and each gas appliance in the property can be treated as a separate offence
• Unlimited fines and up to two years' imprisonment on conviction on indictment in serious cases
• Local authority civil penalties of up to £30,000 per offence under the Housing Act 2004
• Manslaughter charges if a tenant is killed or seriously injured as a result of a gas safety failure caused by neglect — gross negligence manslaughter carries a maximum sentence of life imprisonment

These are not theoretical risks. Several UK landlords have been convicted of manslaughter following tenant deaths from carbon monoxide poisoning in properties without valid certificates. In 2011, the London Borough of Hammersmith and Fulham was fined over £83,000 plus costs by the Health and Safety Executive for failing to carry out annual gas safety checks.

A lapsed certificate also has civil consequences: tenants can withhold rent, councils can issue improvement notices, and a buyer's solicitor will flag a gap in your certificate history during any property sale. The £60–£90 cost of a timely annual inspection is a fraction of any of these outcomes.

Step by step

1. Verify engineer Gas Safe registration

   Before booking anyone, check their Gas Safe registration number at GasSafeRegister.co.uk. Only a current Gas Safe registered engineer can legally carry out a CP12 inspection and issue a valid certificate. Ask for the number before they arrive and cross-check it — registration cards show which types of work the engineer is qualified to carry out.

2. Book the inspection in advance — ideally off-peak

   Do not wait until your certificate is about to expire. Book two to three months ahead, ideally in summer, to get a better price and avoid the autumn rush. If you have multiple properties, contact two or three local engineers and ask for a block-booking rate.

3. Prepare the property before the visit

   Ensure every gas appliance is accessible and working, that the tenant is aware of the appointment, and that there is clear access to the boiler, meter and any gas fires. Check that your boiler pressure is between 1 and 1.5 bar — a cold-system pressure below 1 bar can slow the inspection down and may indicate a fault. If the pressure is low, you can top it up via the filling loop (refer to your boiler manual or the BOYLA pressure guide for your model). Clearing the area around the boiler and any gas fires avoids delays on the day.

4. Be present or arrange access for the engineer

   You or a trusted representative should be available to give the engineer access to every part of the property. The engineer needs access to all appliances, meters and flue terminal points, which may include roof-level or external locations. An abortive visit will usually be charged at a call-out rate.

5. Review the certificate on the day

   Check that the completed Landlord Gas Safety Record includes all required fields: inspection date, property address, landlord details, engineer name and Gas Safe number, each appliance inspected with its location and result, any defects noted, and the engineer's signature. If any field is blank, ask the engineer to complete it before they leave. An incomplete certificate is not legally valid.

6. Provide a copy to your tenant within the legal deadline

   Give existing tenants their copy within 28 days of the inspection. If you have a new tenant moving in, they must receive the certificate before their tenancy begins — not within 28 days, but before they move in. Email delivery is acceptable if you have the tenant's consent. Keep a record of when and how you sent it.

7. File the record and set your next renewal reminder

   Keep the Gas Safety Record for at least two years, even after a subsequent check has been carried out. Store it somewhere you can retrieve it quickly — a solicitor, council officer or court can request it. Set a calendar reminder for 10 months' time so you book next year's inspection in plenty of time.

8. Arrange any remedial work immediately

   If the engineer has identified an At Risk or Immediately Dangerous appliance, arrange repair or replacement with a Gas Safe registered engineer as a priority. Do not attempt to fix gas components, relight an isolated appliance or bypass a safety device yourself. Until remedial work is certified as complete, the affected appliance cannot legally be returned to service in a tenanted property.

Typical costs

Typical UK ranges as a guide only — prices vary by region (expect the top end, or 20–30% more, in London and the South East) and by how accessible your system is. Always get a written quote.

Frequently asked questions