A gas safety certificate is not a boiler service.
Here is the difference.

A landlord gas safety inspection is a safety check of every gas appliance, flue and the pipework in the property, and it produces a Gas Safety Record (the CP12) that the law requires every 12 months. A boiler service is maintenance: the boiler is opened up, the components are cleaned and inspected, the readings are taken and anything drifting is corrected, all to the manufacturer's instructions. The inspection tells you the appliance is safe today, the service is what keeps it that way, and it is the service that most manufacturers ask for every year to keep the warranty valid.

Think of it like a car. A car can have an MOT done and it can have a service done, but an MOT is not a service. The MOT checks that the vehicle is safe and roadworthy, and in the same way a gas safety inspection checks that the gas installation is safe to use, but it does not service the appliances.

What the
inspection covers

The inspection checks that each appliance the landlord provides is operating at the right pressure, that the flue is sound and terminating correctly, that the ventilation is adequate and the safety devices work, that the visible pipework is in good condition, and that the installation holds a tightness test. Nothing is dismantled. If the boiler passes, it is recorded as safe; if it fails, the record says why and the repair is a separate job. We have written up what is checked on a gas safety inspection in more detail.

What the
service covers

A service is the boiler's annual maintenance, done to the manufacturer's own procedure for that model. The case comes off. The heat exchanger, the burner, the fan, the condensate trap and the ignition components are inspected and cleaned as the instructions require, the seals are checked, the flue gas readings are taken with an analyser and compared with the figures the manufacturer gives, the system pressure, the expansion vessel and the magnetic filter are checked, and anything that is on its way out gets mentioned before it fails in January. The service is what the warranty asks for. Most manufacturers' guarantees are conditional on an annual service by a Gas Safe registered engineer, with the Benchmark log completed, and a missed service can give the manufacturer grounds to refuse a claim, so it is worth checking the terms for your own boiler, as they do vary.

Why landlords book both in
one visit

For a rented property the practical problem is access. Every visit means a tenant who has to be in, a key that has to be arranged, and a morning that somebody loses. Doing the inspection and the service in one visit means one set of arrangements, one journey and one record for the file, and the certificate is issued the same day as the service. It is also cheaper than two visits, because the travel and the setting up only happen once, which is why we price the two together when you book them together.

The other reason is less obvious. An inspection on its own can pass a boiler that is a year away from a breakdown, because the inspection asks whether it is safe, not whether it is well. The service is where the fan bearing, the tired expansion vessel or the blocked condensate trap gets noticed, and for a landlord that is the difference between a planned repair in the autumn and an emergency call from a tenant with no heating in the cold.

What to ask for when
you book

Say which of the two you want, or that you want both. Ask whether the service is done to the manufacturer's instructions with the flue gas readings taken, whether the Benchmark log will be completed, and whether the Gas Safety Record is issued on the day. If you have several properties, say so, because they can usually be done on the same day. And check the engineer's registration at https://www.gassaferegister.co.uk, which takes a minute and settles the question that matters most.

The short version

An inspection is a safety check and a legal record, required every 12 months for a rental property. A service is the boiler's annual maintenance, required by most manufacturers to keep the warranty. Landlords book both in one visit because it means one access arrangement, one journey, a lower combined price and a boiler that has been looked after as well as checked.

Quick answers