Sellers photograph the frame number when creating a listing. That number is cross-checked against UK stolen-bike databases used by UK police forces. A match blocks the listing; a clean record publishes it with a verification badge.
How Serial Number Verification Works
Every listing on Cyclesite is automatically checked against the UK's main stolen-bike databases before it can go live. The check runs in the background the moment a seller submits a listing, there is no extra step and no delay for honest sellers.
What the Check Looks For
When a listing is submitted, Cyclesite extracts the frame number from the seller's input and runs it against:
- UK stolen-bike databases. The UK's national cycle database, endorsed by every police force. Holds both owner-registered bikes and stolen reports.
- UK stolen-bike databases. The UK's national property register used by police when recovering stolen goods.
If the frame number matches a stolen report on either database, the listing is blocked automatically. Our Trust and Safety team reviews the match, contacts the seller for evidence of ownership, and either releases the listing or confirms it as stolen.
What Happens if a Listing is Flagged
- Listing paused. It cannot be published, messaged or purchased while the flag is active.
- Seller contacted. We ask for proof of ownership, original purchase receipt, previous UK stolen-bike databases registration, or a statement from the original buyer if the bike has changed hands.
- Investigation. Most flags are resolved within 24 hours. Confirmed stolen bikes are reported to the original registered owner and the relevant police force; the seller's account is suspended pending further review.
- Honest mistake releases. If the flag is a false positive (for example, a frame number reused across years by the manufacturer, or a bike that was recovered and deregistered) the listing is released and goes live.
What the System Does Not Catch
Automatic checks are a safety net, not a guarantee. They cover:
- Bikes stolen in the UK and reported on one of the two main registries.
- Frame numbers provided honestly by the seller.
They do not cover:
- Bikes stolen before widespread registry adoption (roughly pre-2015).
- Bikes stolen overseas and trafficked into the UK.
- Frame numbers that have been altered or removed.
- Bikes stolen but not reported by the owner, an estimated 30% of UK bike thefts go unreported to police.
Your Own Verification
For any bike over £1,000, a buyer verification adds a layer of protection the automatic check cannot. See [How to check if a bike is stolen](/help/buying/check-stolen) for the full routine, frame-number location, databases to search, what to ask the seller, and red flags that should end the conversation.
What To Do If You Suspect a Bike is Stolen
If something is off, the frame number is obscured, the seller is evasive, or the price is implausibly low, do not proceed with the purchase. Report the listing through Report this listing on the listing page, or email safety@cyclesite.co.uk with the listing URL and your concerns. Reports are confidential. Your identity is never shared with the seller.
See [Reporting suspicious listings](/help/safety/report-listing) for what happens after a report is submitted.
Frequently asked questions
Does Cyclesite check every listing for stolen bikes?
Yes. Every listing runs an automatic frame-number check against UK stolen-bike databases before it can go live. If the frame number matches a stolen report, the listing is blocked immediately and our Trust and Safety team investigates.
Which databases do you check?
The UK stolen-bike databases used by every police force, plus the national property register for recovered stolen goods. For high-value listings we also carry out additional proof-of-ownership checks.
What if the seller will not share the frame number?
Walk away. A genuine seller has nothing to hide, frame numbers are stamped into the frame and visible on the listing is normal practice. A refusal, or a ground-off frame number, is the single biggest red flag in used-bike buying.
Does the automatic check cover bikes stolen overseas?
No. UK stolen-bike databases are UK-only. If you are buying a bike that was new outside the UK, we recommend an independent serial search on the manufacturer's database and the international registry if one exists.
Can I verify the frame number myself?
Yes, and we recommend it on any purchase over £1,000. Search the frame number against the UK stolen-bike databases used by police forces. See [How to check if a bike is stolen](/help/buying/check-stolen) for the full routine.