Dear DD
Currently, there is no need to have the extinguishers installed by service engineers (this will change in a few months, by the way, when the new British Standard comes out). The invoice is the proof of installation date and the extinguishers have the manufacturing date stamped on them. After one year you will need to have your extinguisher professionally serviced if you are a business or landlord.
We do however, recommend that you visually inspect the extinguisher (handle not damaged, security pin moves freely and pressure gauge in green) and record the weight. This will help the service engineer in a year’s time tremendously.
Kind Regards
Garry