What is a CP12? Gas Safety Certificates Explained for UK Landlords (2026)

A CP12 — officially the Landlord Gas Safety Record — is the certificate a Gas Safe registered engineer issues after the annual gas safety check that UK landlords are legally required to arrange for every rental property with gas appliances or flues.

If you have just bought your first buy-to-let, or a letting agent has asked you for "the gas cert", this guide covers everything you need to know: what the document is, what the law actually says, what must be written on it, what it costs you to ignore, and what should happen after the engineer packs up.

What a CP12 actually is

The CP12 is a one-page record of a safety inspection. Once a year, a qualified engineer visits the property, checks every gas appliance and flue that you (the landlord) provide, and records the results. The document that comes out of that visit is the Landlord Gas Safety Record — the CP12.

The name is a leftover from history. Before 2009, gas engineers were registered with CORGI, and the standard form for this record was CORGI Proforma 12 — CP12 for short. CORGI was replaced by the Gas Safe Register in April 2009, but the industry never stopped using the old name. If you hear "gas safety certificate", "landlord gas certificate", "LGSR", or "CP12", they all mean the same document.

One important distinction before anything else: a gas safety check is not a boiler service. The check confirms each appliance is safe to use; a service is maintenance that keeps the appliance running efficiently. Many landlords book both in one visit — sensible, and usually cheaper — but a service on its own does not produce a CP12, and a CP12 on its own does not mean the boiler has been serviced. Our CP12 cost guide covers how combined visits are usually priced.

The legal requirement: Gas Safety Regulations 1998

The obligation comes from the Gas Safety (Installation and Use) Regulations 1998, enforced by the Health and Safety Executive (HSE). Regulation 36 places three duties on landlords letting residential property:

1. Annual checks. Every gas appliance and flue you provide for tenants must have a safety check at least every 12 months, carried out by a Gas Safe registered engineer.
2. Records. You must keep a record of each check — the CP12 — and retain it for at least two years.
3. Copies to tenants. You must give a copy of the record to each existing tenant within 28 days of the check, and to any new tenant before they move in.

The duty applies to private landlords, landlords letting through an agent (you can delegate the arranging, not the legal responsibility — check your management contract says who books it), HMO landlords, and people letting holiday accommodation. It applies whether the let is a whole house, a flat, or a room.

The engineer must be on the Gas Safe Register for the type of work involved. Anyone can claim to be "qualified"; the register is the only thing that counts. Ask to see the engineer's ID card and check the back — it lists the categories of gas work they are registered for. You can also verify them at gassaferegister.co.uk.

What the engineer checks on the day

A gas safety check typically takes 30 to 60 minutes depending on the number of appliances. For each appliance and flue the engineer will:

• check the appliance burns gas correctly, measuring operating pressure or heat input
• confirm there is adequate and unobstructed ventilation
• test that flues and chimneys are safely removing the products of combustion
• check safety devices work — that the appliance shuts off as it should when something goes wrong
• carry out a tightness test at the meter to confirm there are no leaks in the pipework

Each appliance gets a result. If something is wrong, the engineer classifies the fault: Immediately Dangerous (ID) — a live risk, and the engineer will ask permission to disconnect the appliance; At Risk (AR) — a fault that could become dangerous; or Not to Current Standards (NCS) — safe, but installed to an older standard. ID and AR findings come with a warning notice, and the defect and the action taken are recorded on the certificate itself.

The 12-month renewal rule

A CP12 is valid for 12 months from the date of the check. Since 2018 the renewal timing has worked like a car MOT: if the next check is carried out in the final two months of the current certificate, the new certificate runs 12 months from the old expiry date — not from the day of the check.

That means renewing early inside that window costs you nothing, and the expiry date becomes a fixed anniversary for the property. The practical advice is simple: book the check at the start of month 10 or 11, and the remaining weeks become slack for tenant access problems, holidays, and rebooking, rather than a deadline. We cover the timing rule in detail in CP12 renewal rules.

If the certificate has already expired, arrange a check immediately — the property is non-compliant for every day of the gap, and the new certificate will run from the date of the new check.

What must be on the certificate

The regulations set out the minimum information a CP12 must contain. A valid record includes:

• the date the check was carried out
• the address of the property
• the landlord's name and address (or the letting agent's, where the agent manages)
• a description and location of each appliance and flue checked
• the results of the check for each appliance, including any safety defect identified and the action taken to fix it
• confirmation that the check covered the matters the regulations require (combustion, ventilation, flue operation, safety devices)
• the name, registration number and signature of the engineer who did the check

A missing landlord address or an unrecorded appliance can render the record useless as evidence of compliance, even though a check physically happened. When you receive your copy, it is worth thirty seconds to confirm every appliance you provide is listed and the landlord details are yours. Digital records are fine — there is no requirement for paper or a wet-ink signature — as long as the content is complete and tenants can receive their copies.

Penalties for not having one

Failing to comply with the gas safety regulations is a criminal offence. Enforcement sits with the HSE, and the consequences scale with the seriousness of what went wrong:

• Prosecution and fines. Breaches can be prosecuted in the magistrates' court or the Crown Court, where fines are unlimited. Courts treat gas safety failures seriously because the risk — carbon monoxide poisoning, fire, explosion — is to life.
• Imprisonment. In the most serious cases, custodial sentences are available, and where a tenant dies, landlords have faced manslaughter and corporate manslaughter charges.
• Insurance problems. Many landlord policies assume you are meeting statutory obligations. A lapsed certificate can complicate or void a claim after a gas-related incident.

A gas safety record can also matter beyond HSE enforcement: compliance documents are routinely tested in possession proceedings, and recent changes to the possession rules in England have made landlords' paperwork more scrutinised, not less. Take specific advice on your situation rather than relying on general summaries — including this one.

The cheapest possible view of a CP12 is this: the check itself costs less than one week's rent for most properties, and the downside of not having one is uncapped.

How you receive the certificate — and who you must give it to

The engineer completes the record and gives it to whoever instructed the work — you or your letting agent. With paper pads that historically meant a carbon copy left at the property and one posted on; today most engineers issue a PDF by email, or send a link where the certificate can be downloaded, sometimes with a permanent per-property page that holds the current certificate and its renewal date.

From the moment you have it, three deadlines are yours:

1. Existing tenants must receive a copy within 28 days of the check.
2. New tenants must receive a copy before they move in.
3. You must keep each record for at least two years (in practice, keep everything — a complete history costs nothing to store digitally).

If your agent manages the property, confirm in writing who sends copies to tenants and who stores the records. "I assumed the agent had it" is one of the most common ways a landlord ends up unable to produce a certificate when it matters. However you receive yours, store it against the property — not in an email thread — and put the renewal date somewhere that will actively remind you, rather than somewhere you would have to remember to look.

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