How do I check a bike serial number?
Direct answer · Cyclesite
A bike's serial number, also called the frame number, is the unique code stamped into the frame at manufacture, and it is the single most useful identifier for checking a bike's history. On most bikes it is stamped underneath the bottom bracket, the shell where the two crank arms meet, so you read it by turning the bike upside down or lifting it overhead. On some frames it sits instead on the head tube at the front, the rear dropout near the wheel, the underside of the down tube, or the seat tube. Once you have found it, write it down exactly, including letters and zeros, and check it against the UK stolen-bike databases. Cyclesite's free stolen-bike check does this in seconds: enter the frame number and it cross-references the national registers that police and insurers use, returning a clear, stolen or caution result. If you own the bike, recording its serial number now, with a clear photo, is the most valuable thing you can do, because police can only return a recovered bike to you if its number is on record.
Last reviewed: 2026-07-16
Where to find the serial number
Start under the bottom bracket: turn the bike over and look at the shell between the pedals, where most manufacturers stamp the number. If it is not there, check the head tube at the front, the rear dropout where the back wheel sits, the underside of the down tube, and the seat tube. The number is usually a mix of letters and digits, so note it down exactly, because a single mistaken character (an O for a 0) will throw off any check.
How to check it for free
Once you have the number, run it through Cyclesite's free stolen-bike check. It cross-references the national stolen-bike registers in seconds and returns one of three outcomes: clear (no match), stolen (reported on a register), or caution (a partial or uncertain match worth investigating before you buy). Doing this before any money changes hands is the simplest way to avoid unknowingly buying stolen property.
Why you should record your own
A serial number is only useful for recovery if it is written down somewhere before the bike is stolen. Photograph your frame number, store it with your purchase receipt, and register it on a stolen-bike register. If your bike is later taken and recovered, police match the number on the bike to the owner on the register. Without that record, a recovered bike often cannot be returned.
Average used bike prices by category (UK)
| Category | Average price | Sample size |
|---|---|---|
| road | £1,477 | 13 |
| ebike | , | 6 |
| mtb | , | 3 |
| gravel | , | 2 |
| bmx | , | 1 |
Last updated: 2026-07-16
Related Questions
Where is the serial number on a bike?
Most often underneath the bottom bracket, the shell where the crank arms meet the frame. It can also be on the head tube, rear dropout, down tube or seat tube depending on the manufacturer.
Is checking a bike serial number free?
Yes. Cyclesite's stolen-bike check is free: enter the frame number and it cross-references the UK stolen-bike registers in seconds, returning a clear, stolen or caution result.
What if the serial number has been removed?
A filed-off, scratched or painted-over serial number is a serious warning sign: treat it as a reason to walk away. A legitimate seller has no reason to obscure it, and a missing number makes the bike impossible to verify or recover.
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