What a proper CP12 inspection includes
Tightness test at the gas meter to detect leaks in the pipework. Every gas appliance in the property visually inspected and combustion-analysed with a calibrated flue gas analyser. Flues inspected for integrity and correct termination. Ventilation checked against appliance requirements. Safety devices (flame supervision, oxygen depletion sensors, TRVs on cookers) operationally tested. Standing and working pressures recorded. Any 'immediately dangerous' or 'at risk' findings actioned and documented.
Landlord obligations under the law
Under the Gas Safety (Installation and Use) Regulations 1998, landlords must have every gas appliance and flue inspected annually by a Gas Safe engineer, keep records for 2 years, and provide a copy of the current Gas Safety Record to tenants within 28 days of the inspection and to new tenants before they move in.
The 10–12 month renewal window
You can carry out the inspection any time in the 2 months before expiry without losing the 12-month validity, renew in month 11 and the new certificate is valid until 12 months after the old one expired, not 12 months after issue. Useful for keeping annual dates consistent.
Homebuyer and pre-purchase inspections
Not legally required for buyers, but strongly advisable. A homebuyer inspection identifies dangerous or expensive-to-fix appliances before you commit, occasionally material to price negotiation, always useful for peace of mind.
Combining with an annual boiler service
For landlords, combining the Gas Safety inspection with an annual boiler service is efficient, one visit, one fee, both documents issued. Also keeps the boiler warranty protected.