What Is a CP12 Certificate? The Landlord's Plain-English Guide

Where the Name Comes From

CP12 stands for "CORGI Proforma 12" — a form number from when the Council for Registered Gas Installers (CORGI) ran the gas registration scheme. CORGI was replaced by the Gas Safe Register in April 2009, but the name stuck. Engineers, letting agents, and council licensing teams still call it a CP12 even though it has no statutory basis under that name.

The legal document is a Landlord Gas Safety Record, prescribed by Regulation 36(3)(c) of the Gas Safety (Installation and Use) Regulations 1998. There is no mandated physical layout or official template. Any document — paper or digital — that captures all the required fields satisfies the law.

What a Valid CP12 Must Contain

Nine statutory fields must appear on the record:

1. The date of the inspection
2. The full postal address of the property
3. The landlord's (or managing agent's) name and address
4. A description and location of every appliance and flue checked
5. Details of any safety defects found
6. What remedial action was taken
7. A statement confirming the check meets GSIUR requirements
8. The engineer's name and signature
9. The engineer's Gas Safe registration number (a 7-digit number)

Omit any one of these and the record is invalid for statutory compliance purposes, regardless of whether the physical check was done properly. Before you pay the invoice, walk through all nine fields.

CP12 vs Boiler Service vs Installation Certificate

These three documents serve different legal purposes:

A CP12 / Landlord Gas Safety Record confirms the annual safety check under Regulation 36. It verifies gas tightness, burner pressure, flue flow, combustion performance, and safety device operation across every landlord-provided appliance.

A boiler service is a manufacturer-specified maintenance procedure to keep the appliance running efficiently. An engineer can perform both during the same visit, but the service invoice alone doesn't replace a CP12 unless it contains all nine statutory fields.

An installation certificate (such as a Benchmark Logbook entry) documents that a new appliance was correctly fitted. It satisfies Building Regulations Part J notification requirements but has nothing to do with the ongoing annual inspection duty.

The key distinction: a boiler service keeps the machine healthy, a CP12 keeps you legal.

What Happens During the Check

The engineer tests each gas appliance and its associated flue. A typical single-boiler check takes 20 to 40 minutes and covers:

• Gas tightness of the installation pipework
• Burner pressure and gas rate
• Flue flow and spillage tests
• Combustion gas analysis
• Safety device operation (thermocouples, flame supervision)
• Visual inspection of the flue terminal and ventilation

If the engineer finds a defect, they classify it under the industry's Unsafe Situations Procedure: Immediately Dangerous (gas disconnected on the spot), At Risk (appliance turned off pending repair), or Not to Current Standards (noted for future upgrade but not an immediate hazard).

Why It Matters Beyond the Check

A CP12 is the proof that sits between you and an unlimited fine. Some local councils require it for HMO and selective licensing applications; check the conditions for your area. The national PRS Database rolling out from December 2026 will require a copy of the gas safety record and its issue date as part of the dwelling entry. And if a tenant ever disputes your compliance, the record — with its nine fields, engineer credentials, and your delivery proof — is the document you'll produce.

For the complete process from booking to delivery to retention, our Gas Safety Compliance Guide lays it out step by step.

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