Boiler warranties: what actually voids them
10 years sounds great until you read the conditions. The three things that void most warranties, and how to keep yours alive.
Updated 16 August 2026 · 2 min read
A 10-year warranty is one of the main reasons people pay more for a premium boiler. It's worth having. It's also conditional in ways most people never read.
The three things that void it
No annual service. This is the big one. Miss a single year and most manufacturers will refuse a claim, no matter how minor the fault.
No magnetic filter. Many warranties now require one fitted at installation. If it wasn't on your quote, that warranty may already be worthless.
Not registered. The boiler has to be registered with the manufacturer within a set window, commonly 30 days from installation. Plenty of installers do this for you as a matter of course, but it is a condition of the guarantee rather than a legal duty of theirs, so if it does not happen it is your loss. Ask on the day whether they are registering it or whether you are.
The service record is the evidence, not the service
Having the service done is only half of it. What a manufacturer asks for when you claim is proof, and the proof is the Service Record inside the Benchmark booklet that came with the boiler.
Worcester Bosch, to take one example, states in its own user instructions that a call-out charge will be made where evidence cannot be provided that the first year service inspection has been carried out, meaning an entry in the Benchmark Checklist. A serviced boiler with an unstamped book looks identical to an unserviced one from where the manufacturer is sitting.
So every year, before the engineer leaves, make sure the Service Record has been filled in and signed. It takes half a minute and it is the whole difference between a covered repair and a bill.
What the service actually costs
One visit a year, and it is one of the cheapest things you will ever pay a Gas Safe engineer to do. Over ten years it still adds up to a real sum, and what it is protecting is both the boiler and a warranty worth considerably more than the servicing.
Which means a 10-year warranty is really a 10-year warranty plus ten annual services. Factor that in when you're comparing a boiler with a 5-year warranty against one with 12, and ask each installer what their service costs.
Parts and labour, or just parts?
Read this bit. Some warranties cover parts only, and you pay the engineer's call-out and labour. Others cover both. On a single visit that difference is substantial, and it repeats every time something goes wrong.
Ask the installer which one you're getting, and get the answer in writing on the quote.