How to check your boiler warranty

The short answer

A boiler warranty check is really three checks. How long the warranty was meant to run, whether it was ever properly activated, and whether it has stayed valid since. It is easy to do only the first, then find out the hard way that the other two decided it.

The serial number is the key to all of it. Every major manufacturer runs a checker or a customer service line that takes it and tells you where you stand. Worcester Bosch's guarantee checker asks you to enter your 23 digit serial number to find your guarantee expiry date. Vaillant asks for a 28 digit serial number, and Glow-worm uses the same format.

What you need before you start

• The serial number. Every manufacturer asks for this one.
• The installation address and postcode. Warranties are registered against a property.
• The installation date, if you know it.
• Your annual service records, which decide whether the warranty is still valid.

Step 1: find the serial number

Manufacturers put the serial number in different places, which is why people give up here. Worcester Bosch says outright that different products keep their serial numbers in different places, and warns you not to remove screws or get into restricted areas looking for one.

There is usually a second copy on paper. Vaillant points out that the number is also in the Benchmark logbook your installer should have handed over, and Ideal Heating says the same about its Benchmark certificate.

Never open the boiler casing to hunt for it. Behind that panel is gas work, and only a Gas Safe registered engineer may touch it.

Where the serial number is, and where to check

Step 2: run the number through the manufacturer

This is the only check that counts. A plumber's guess or the length quoted on a comparison site will not tell you what your boiler is registered for.

Worcester Bosch is blunt about inherited boilers: find the serial number, get in touch and share it, and Worcester will tell you whether the boiler is still under guarantee. The lookup works even if you were not the one who registered it, though what comes back still depends on whether it was registered at all.

Write down two dates: the expiry date, and the registration date.

Step 3: check it was registered in time

The five biggest UK brands all work the same way here. Worcester Bosch, Vaillant, Ideal Heating, Baxi and Glow-worm each give you 30 days from installation to register, and each one shortens or withdraws the guarantee if that window is missed. Check your own manufacturer's terms, because the penalty is not identical across the market. This is where long warranties quietly become short ones.

What you lose depends on the make. Vaillant states that the guarantee must be registered within 30 days of installing the appliance, and that failure to register in that period results in the guarantee reverting to 12 months from the date of installation. Glow-worm applies the same rule. Ideal Heating says the boiler must be registered within 30 days to qualify for the full guarantee, and that missing it reduces the period of guarantee to 12 months. Worcester Bosch and Baxi both require registration within 30 days too, but do not publish that same flat 12 month fallback, so read their guarantee terms for what you would actually be left with.

So a boiler sold on a 10 year warranty can be sitting on 12 months because nobody filled in a form, and that is a common reason a check comes back short. If the boiler went in less than 30 days ago and nothing has been registered, register it now: most manufacturers let either the installer or the homeowner do it.

Step 4: check it has stayed valid

A registered warranty is not a permanent one. Two conditions keep it alive, and both sit with you.

The annual service is the big one. Worcester Bosch's guarantee checker carries the condition in plain sight: all dates and guarantee validity of boilers are subject to an annual service being undertaken every year since installation. Vaillant requires the boiler to be serviced annually by a Vaillant or other Gas Safe registered engineer in accordance with the manufacturer's instructions, and Baxi lists an annual service among its warranty conditions. Miss a year and you may have nothing to fall back on, even inside the warranty period.

The Benchmark checklist is the other, and it was decided on day one. Benchmark is the industry commissioning scheme run through the Heating and Hotwater Industry Council, launched in 1999. The checklist is completed in full by the competent person who commissioned the boiler, then handed to the customer to keep. The scheme's own wording is that failure to commission to the manufacturer's instructions and complete the checklist will invalidate the warranty, though it does not affect your statutory rights.

One more trap. In warranty, the repair usually has to go through the manufacturer. Vaillant covers material and labour on boiler components provided Vaillant or a Vaillant authorised Gas Safe registered engineer carries out the repair, and Worcester Bosch will not reimburse third party costs unless it authorised the work in advance and in writing.

Finding the installation date if you do not know it

Warranty length runs from installation, so if you moved into a house with the boiler already in it, that date is the missing piece. Two places carry it.

The Benchmark checklist or logbook is the first. Sellers often leave it in a drawer near the boiler, and it holds the commissioning date, the installer's details and the serial number.

The Gas Safe Register is the second. In England and Wales, a Gas Safe registered business installing a heat producing appliance such as a boiler must notify it to the relevant local authority within 30 days of installation, and Gas Safe Register lets you search online to see whether an installation at your address was notified. You should also have a Building Regulations Compliance Certificate for the property, issued after that notification. If nothing was notified, Gas Safe Register's advice is to go back to the business and ask them to notify the work. The rules are different in Scotland and Northern Ireland, so if your home is there, check what your own building control regime expected of the installer.

What to do when the warranty has run out

Once the warranty has gone, the cost of a breakdown usually falls to you. A cover plan is one way to handle that. It is not the only one: as the Benchmark scheme's own wording puts it, none of this affects your statutory rights.

A warranty and a cover plan are not the same thing. A manufacturer warranty comes with the boiler, is included in what you paid for it, and deals with defects in the boiler as built, though keeping it alive costs you an annual service every year. A cover plan is a service you pay for monthly, covering future breakdowns on the modules you choose. If your boiler is still in warranty, use the warranty: a cover plan fills the gap afterwards. Our separate guide, boiler warranty vs boiler cover, sets out line by line what each one actually pays for, and it is linked at the foot of this page.

Here is the honest shape of ours. The boiler and central heating module covers parts and labour, capped at £500 in any 12-month period when the boiler is under 7 years old and £200 when it is over 7. Anything above the cap you pay yourself. Booked call-outs are Monday to Friday, 08:00 to 18:00, and we aim to get an engineer out to you within two working days. Four situations carry a £95 call-out fee, paid in advance: anything reported in your first 30 days, anything the plan does not cover, a visit where nobody is home, and an annual service asked for early. Cover itself is running throughout those first 30 days, so the fee is the only difference. A fault your boiler already has is pre-existing, and pre-existing faults are not covered. Payment is monthly, but the first time you use a service a 12-month agreement period begins, and leaving inside it costs the remaining months or 75% of the outstanding balance. We work with a national network of thousands of Gas Safe registered engineers. Smart Plan is a service plan, not insurance, from UK Boiler Company Ltd, trading since 2014.

One safety point sits above all of this, warranty or no warranty. A boiler burns gas. If you ever smell gas in the house, leave the electrics alone, no switches on or off, no cigarettes and no naked flames of any kind, get the windows and doors open, and ring the National Gas Emergency Service on 0800 111 999 before you do anything else.

Boiler warranty check FAQs

Warranty run out? Tell us about your boiler.

Parts and labour on the boiler and central heating module are capped at £500 in any 12-month period under 7 years old, £200 over 7. The £95 call-out fee, paid in advance, applies in the first 30 days, to uncovered faults, no-access visits and early annual services, and your cover is live throughout those 30 days. Cover runs monthly, and a 12-month agreement period starts the first time you use a service. Smart Plan is a service plan, not insurance.

Helpful links

• Boiler warranty vs boiler cover: what each one pays for
• What a boiler warranty does not cover
• Boiler & central heating cover
• Checking a boiler before you buy a house
• Worcester Bosch guarantee explained
• Building Regulations certificates on the Gas Safe Register
• Worcester Bosch guarantee checker
• Vaillant guarantee registration