BS 3621 Smart Lock Compliance UK¶

What BS 3621 means for your UK smart lock - certification requirements, insurance implications, and how to verify compliance.

Understanding BS 3621 for Smart Locks¶

BS 3621 is the British Standard that specifies the performance requirements for thief-resistant locks. In 2021, the standard was updated (BS 3621:2021) to explicitly cover electronically operated and motorised deadbolts, bringing smart locks into scope. A BS 3621-compliant smart lock must resist attack by hand tools for 3 minutes, have a minimum 20 mm bolt projection, and include a mechanical key override. The Ultion Keyturn WiFi (£279) and Brisant Secure Smart (£149) both carry BS 3621 certification. The Nuki 3.0 Pro (£179) is not itself BS 3621 certified - it relies on the cylinder achieving TS 007 3-star. Most UK insurers require BS 3621 on all external doors. Failure to comply can void your home insurance - the Financial Ombudsman Service reports approximately 300 cases per year where claims were denied due to non-compliant locks.

How to Ensure Your Smart Lock Meets the Standard¶

To verify BS 3621 compliance, check for the Kitemark on the cylinder body and on the product packaging. The certification number follows the format 'KM 12345'. If buying online, the product page should list the standard in the specifications. Reputable UK retailers such as Screwfix, Toolstation, and B&Q clearly display the certification. For smart locks that use an existing cylinder, the cylinder itself must be BS 3621 compliant - the smart lock body does not need separate certification. The TS 007 3-star rating is increasingly accepted as equivalent by major insurers. Always check with your insurance provider before fitting a smart lock. A written confirmation is recommended. If you own a leasehold property, check the lease terms - some freeholders explicitly require BS 3621 locks.

Specifications and Comparison¶

Standard	Coverage	Key Requirements	Insurance Acceptance
BS 3621:2021	Entire lock assembly	3-min attack resistance, 20 mm bolt, key override	Most UK insurers
TS 007 3-star	Cylinder only	Drill, snap, pick, bump resistance	Widely accepted
Sold Secure Diamond	Lock cylinder	Enhanced attack resistance	Accepted by leading insurers
Secured by Design	Police preferred	Meets Association of Chief Police Officers standards	Some insurers accept

FAQ¶

Does my smart lock need BS 3621 certification?: Most UK home insurance policies require BS 3621 or equivalent on external doors. Check your policy wording - TS 007 3-star is increasingly accepted.
Is the Nuki 3.0 Pro BS 3621 compliant?: The Nuki motor body is not itself certified. Compliance depends on the Euro cylinder paired with it. Use a TS 007 3-star cylinder to meet insurance requirements.
What changed in BS 3621:2021 for smart locks?: The 2021 revision explicitly covers electronic and motorised locking mechanisms. It requires that smart locks maintain mechanical key override and meet the same attack-resistance tests. For more information see our Smart Lock Security Ratings UK.

Last updated: 2026-05-31.

External Resources¶

For further information consult authority guidelines at the Ofcom.