It is highly recommended that you have your appliance serviced by a qualified Gas Safe registered engineer once a year.
There are two types of maintenance checks, namely a safety inspection and a service. In a safety inspection the engineer will typically carry out a visual inspection of any gas appliances (i.e. boiler/gas hob/gas fire, etc.), check the air supply is adequate, the flue is functional and the boiler is burning gas correctly/efficiently, and that any safety devices are operating correctly. You could think of this as like an MOT for your car, it simply proves that it passes a safety inspection on that day. It’s worth noting that landlords are legally obliged to have a gas safety inspection on the gas appliances within a rental property at least every 12 months.
A boiler service is more thorough as the engineer will not only carry out safety tests but will also check internal components for wear and carry out cleaning and adjustments where necessary. Most boiler manufacturers state that a boiler service should be carried out at least every 12 months to maintain the boiler warranty.
If possible, Summer is a good time to have these checks as demands on your boiler will be lighter and repairs will cause less inconvenience than in Winter. However, if at any other time you notice signs that the boiler might not be functioning properly, you should have it checked right away.
For further information on this topic, please take a look at the importance of annual servicing.