Every four years, canal and river boats must undergo a safety check by an authorised inspector. The “BSS” remit seems to expand gently every few years as potential hazards are identified from experiences on the waterways. Mostly though, it’s about ensuring your boat is not a hazard to yourself or to other craft and so includes assorted checks on any propane gas tanks, pipes and devices such as your cooker. The diesel system will be inspected too, as well the battery bank which must be suitably secured against motion in all directions.
Full details of the BSS and comprehensive information about what you need to do to pass the test can be found on the BSS website, run by the CRT and Environment Agency. A BSS costs probably a couple of hundred pounds, which once every four years is not too horrific all things considered.
If you’re buying a boat, make sure it has a current BSS and if you’re selling, it can be a good reassurance to buyers if you get a new BSS. It’s a bit like an MoT inspection on a car.
 For overseas readers, the “MoT” test is an annual check of vehicles over three years old for their general roadworthiness. The Ministry of Transport, after which it was named, has long since been given another title but the ‘MoT” moniker remains.