Read your own policy wording first, because insurers set their own standards. Most ask for a BS 3621 lock on timber doors – usually a five-lever mortice deadlock with the kitemark stamped on the faceplate – and a TS 007 3-star or SS 312 Diamond cylinder on uPVC and composite doors. Check the markings on your locks, and keep the invoice if you upgrade.
Why insurers care about your locks
Home insurance policies almost always include a minimum security clause. It names the lock standards your doors must meet, and if your locks fall short, a theft-related insurance claim can be reduced or refused. The same minimum security clause appears in both buildings insurance and contents insurance policies, so it applies however you bought your cover. Comparison site Uswitch is blunt about it: if your locks do not comply with your policy, you risk invalidating a claim. The AA similarly notes that insurers can refuse claims where the named security standard was not in place.
The uncomfortable part is that most people never check. The policy wording sits unread, the locks stay as they were when the previous owner fitted them, and the mismatch only comes to light at the worst possible moment. Ten minutes with your policy and a torch fixes that.
The standards, in plain English
There is no single “insurance approved” lock. The phrase usually means a lock meeting the British Standard your policy names. Some policies extend the same idea to window locks on accessible windows; your own wording decides. These are the lock markings you will come across:
| Marking | What it is | Where you find it |
|---|---|---|
| BS 3621 | British Standard for thief-resistant key-operated locks. Usually a five-lever mortice deadlock; some night latches also carry it | Kitemark and “BS 3621” stamped on the faceplate, the metal strip on the door’s edge |
| TS 007 | Cylinder and handle star-rating from the Door & Hardware Federation. A 3-star cylinder alone, or a 1-star cylinder with a 2-star handle, gives anti-snap protection | Stars and kitemark on the face of the cylinder |
| SS 312 Diamond | Sold Secure’s top grade for euro cylinders | Diamond logo on the cylinder face |
| PAS 24 | A test of the whole door or window set, not just the lock | Applies to new doors and windows; not something a locksmith can add to an existing door |
For timber front and back doors, insurers typically name BS 3621. For uPVC and composite doors, which use a multi-point locking mechanism with a euro cylinder, they look at the cylinder rating instead: TS 007 3-star or SS 312 Diamond. Our guide to British Standard locks explains what the kitemark means in practice: https://ahlp.co.uk/why-choose-british-standard-locks-better-security/
How to check your locks in five minutes
- Open the door and look at the edge. A mortice deadlock sits inside the door with a metal faceplate. A BS 3621 lock has the British Standard kitemark and “BS 3621” stamped on that faceplate, often with “5 lever” alongside.
- Count the locking points on a uPVC door. Lift the handle: hooks, rollers or bolts should engage at several points up the frame. That is the multi-point mechanism insurers expect on these doors.
- Look at the cylinder face. On uPVC and composite doors, the euro cylinder face should show either three stars with a kitemark (TS 007) or the Sold Secure Diamond mark. No marking means it has not passed the test, whatever the packaging once said.
- Check every external door, not just the front. Insurers’ wording usually covers all final exit doors, and often ground-floor windows too. The back door is the one most people forget.
- Read the policy wording. The exact standard and which doors it applies to is written in your policy documents. If anything is unclear, ask your insurer directly – their answer is the one that counts at claim time.
Stuck on any of these? Send us a photo of each lock and one of the whole door, so we can see what the door is made of, on WhatsApp (07700 100146). We are happy to give guidance for free: what lock is fitted, what standard it appears to meet, and whether it looks to be keeping your home secure. Photos can guide, but they cannot certify – your insurer’s wording is the final word on compliance, and anything a photo cannot settle needs a proper look at the door.
What if your locks do not comply?
Two options, and doing nothing is not one of them. Tell your insurer and see whether the policy can note the locks you have, or upgrade the locks to the standard named. Upgrading is usually the straightforward route. In many cases a mortice deadlock can be swapped for a BS 3621 version using the existing cut-out, and a euro cylinder can often be replaced with a TS 007 3-star one without altering the door. Doors and locks vary, though, so a locksmith checks the door and confirms compatibility before quoting.
On cost, published guides give a useful sense of scale. Checkatrade’s 2026 figures put a fitted anti-snap cylinder at around £150 on average, and industry price lists for 2026 start at roughly £137 fitted. A BS 3621 mortice deadlock fitted typically runs between £100 and £205 depending on the lock and door, per the same published sources. Any reputable locksmith, AHLP included, will confirm the exact price for your doors before any work begins. Our UK lock replacement cost guide has the wider picture: https://ahlp.co.uk/cost-of-lock-replacement-in-the-uk-2026-guide/
Keep the evidence
If you upgrade, ask for the standard to be named on the invoice: “TS 007 3-star cylinder fitted” or “BS 3621 five-lever mortice deadlock fitted”, for example. Keep that invoice with your policy documents. If you ever need to claim, that invoice is your evidence of exactly what was fitted and when. Your insurer still decides whether the policy requirement was met, but a named standard on an invoice is far harder to argue with than your memory of what was on the door.
Will better locks cut your premium?
Sometimes. Uswitch and the AA both note that insurers can look favourably on improved security, and some policies offer a discount where approved locks are fitted, though it is not guaranteed and the saving varies. The bigger prize is simpler: knowing a theft claim will not be refused over a £50 lock. If you are upgrading anyway, our article on anti-snap locks explains what the protection actually does: https://ahlp.co.uk/what-is-anti-snap-lock/
Frequently asked questions
Do I need BS 3621 locks for my home insurance?
Many policies name BS 3621 for timber exit doors, but there is no universal rule – insurers write their own wording and it differs between policies. The only reliable answer for your home is in your policy documents, or from your insurer directly.
Are uPVC door locks covered by BS 3621?
BS 3621 applies mainly to mortice deadlocks and some night latches on timber doors. uPVC and composite doors use a multi-point mechanism with a euro cylinder, so insurers assess the cylinder rating instead: TS 007 3-star or SS 312 Diamond are the marks to look for.
Does a night latch count as an insurance-compliant lock?
Some night latches carry BS 3621 certification, and insurers may accept them alongside – not instead of – a mortice deadlock. A basic night latch on its own is widely treated as a secondary lock. Again, your policy wording decides.
My locks do not meet the standard. What happens if I am burgled?
A theft claim can be reduced or refused if the policy’s security clause was not met. Tell your insurer and either have the policy amended or the locks upgraded, and keep the invoice for any work as evidence.
Can AHLP check and upgrade my locks?
Yes. We can identify what is fitted, tell you what standard each lock meets, and replace locks or cylinders where an upgrade makes sense, with the price confirmed before work starts. We replace locks and cylinders rather than re-keying them, and if your plans change before we attend, we do not charge for that – you only pay for work and parts.
Sources and checks
- Uswitch, door lock types and home insurance guidance: https://www.uswitch.com/home-insurance/door-lock-types/
- The AA, home security and insurance guidance
- Locksmiths Trade, Insurance approved locks: BS 3621 and TS 007 explained (checked 2026): https://www.locksmiths.trade/guides/insurance-approved-locks/
- Door & Hardware Federation, TS 007: https://www.dhfonline.org.uk/
- Checkatrade and industry price lists, anti-snap cylinder and mortice deadlock fitting costs, 2026
Sources checked 24 October 2026. Policy requirements vary – your own policy wording is always the final word.