Bike frame number check: how to do it in four steps

Buying a second-hand bike is often a smart way to save money. But you want to be sure the bike is not stolen. That goes double for a bike bought through Marktplaats (the Dutch classifieds site) or Facebook, or from a seller who has no proof of purchase. A quick frame number check lowers the risk that you unknowingly buy a stolen bike.

In this article you will read where to find the frame number, how to check it, what the result means and how to protect your bike after you buy it.

What is a frame number and where do you find it?

The frame number is the identification number of the bicycle frame, sometimes called the bike's serial number. It is usually engraved or stamped into the frame. With this number you can identify, check and register a bike, and make it easier to recognise if it is ever stolen.

You will usually find the frame number in one of these places:

• Under the bottom bracket: on the underside of the frame, where the pedal cranks meet.
• On the seat tube: the frame tube below the saddle, where the seatpost goes in.
• On the front fork: the part of the bike that holds the front wheel.

The exact spot differs by manufacturer and model. Sometimes the number is elsewhere on the frame. On some bikes it is hard to read because of dirt, paint or wear.

Tip: take a clear photo of the frame number and of the whole bike straight away. Keep them together with the receipt or other documents. That way you always have the details at hand for a check, a police report or your insurer.

How do you check a bike's frame number? Four steps

Step 1. Write down the frame number and collect the bike's details

Copy the frame number exactly. Watch out for characters that look alike, such as O and 0 or I and 1. Note the make, model, type and colour as well. These details help you confirm that the number you found really belongs to the bike on offer.

Also ask the seller for the receipt, warranty card or insurance papers. Compare the frame number on the documents with the number on the frame. Do they differ? Then do not complete the purchase until the difference has been credibly explained. If the difference is suspicious or cannot be explained, walk away.

Step 2. Check the bike in the available registers

There are several ways to find out whether a bike is known as stolen. Stop Heling and the RDW focus on theft reports. BIKEBAZE combines a public status check with the option to register your own bike in your name.

1. Stop Heling: is the bike listed as stolen with the police?

Stop Heling is the Dutch police register of stolen goods, including bicycles. The site has an English version. For a bike, the serial number is the frame number. Enter the number on the website and click Check serial number. The search works with at least five characters of the number.

The register is updated daily and contains goods reported stolen to the police since 1 January 2010. Is a character on the frame hard to read? Check the number again and, if needed, try the plausible variants of that unclear character.

No result does not automatically mean the bike was never stolen. If no police report was filed, or the report has not been processed yet, a stolen bike can be missing from the register.

Check now: Stop Heling.

2. RDW bicycle theft register: check make and frame number

The RDW (Netherlands Vehicle Authority) runs the national bicycle theft register, which anyone can search online. You enter the make and frame number and get yes if the bike is registered as stolen, or no if no registration is found. The search page itself is in Dutch; the English explanation is on government.nl.

The register mainly contains theft reports filed after 1 January 2008. Older reports are only partly included. Keep in mind that the police have up to ten days to verify a report and register the bike as stolen, so a recent theft may not show up yet.

Check now: RDW bicycle theft register.

3. BIKEBAZE: check the status and register your bike

BIKEBAZE is the only accessible bike registry in the Netherlands. Any cyclist can register a bike with BIKEBAZE for free and link it to their own name. You keep the important bike details in one place and can easily transfer the registration when you sell the bike.

BIKEBAZE is more than a list of stolen bikes. With the public BIKEBAZE bike check you look up the status of a bike by its frame number or a linked SafeTag ID. A battery number works too, when it is part of the registration.

How does the link with Stop Heling work? When someone looks up a bike's status through BIKEBAZE, BIKEBAZE automatically checks not only its own bike registry but also the theft status at Stop Heling. On top of that, it checks Bike Index, an international bike registry. Those extra checks happen during the same status check, so you do not have to run a separate search for each register. In practice this is a bike serial number lookup across three sources at once.

You see in one place whether the bike is known to BIKEBAZE and whether any of the theft registers consulted holds a theft report. The registers are not one shared database: BIKEBAZE queries the external sources at the moment you check.

With a BIKEBAZE registration you can store more than the frame number: make, model, colour, photos and the purchase invoice. You get a digital registration file and a PDF proof of ownership based on the details you provide. When you sell the bike, you can transfer it to the next owner through BIKEBAZE. As a private individual you cannot do that through Stop Heling or the RDW register.

BIKEBAZE also works with a community and optional SafeTags: eye-catching, tamper-resistant stickers with a scannable code that are linked to the bike registration. Anyone who finds or checks the bike sees its status straight away and, if it is reported stolen, can send the owner an anonymous message and the location through BIKEBAZE.

Check now: Check a bike with BIKEBAZE. Want to know more about the differences? Read BIKEBAZE vs Stop Heling vs RDW: what are the differences?.

Step 3. What does the result of your check mean?

The bike is registered as stolen

Cancel the purchase. Buying a bike you know, or should reasonably have suspected, is stolen can count as handling stolen goods (heling), a criminal offence in the Netherlands. Report the situation to the police. Did you find the bike through an advert? Keep the relevant details of the advert and the seller for your report. Is the bike reported stolen at BIKEBAZE? Then you can send the owner an anonymous message and share the location through BIKEBAZE, without either of you seeing the other's contact details.

The bike is not registered as stolen

That is a good sign, but no guarantee that the bike was not stolen. Perhaps no police report was filed, a report has not been processed yet, or the number was entered incorrectly. So always compare the bike, the frame number, the documents and the seller's story.

The bike is not known to BIKEBAZE

That only means no matching BIKEBAZE registration was found for the details you entered. On its own it says nothing definitive about where the bike came from or who owns it. After the purchase you can create a registration yourself right away.

Step 4. Check for red flags and decide whether to buy

Even if the online checks show no theft report, take a good look at the bike yourself. Watch out for these signs in particular:

• The frame number has been scratched out, ground off, painted over or re-stamped.
• The seller will not or cannot show you the frame number.
• There is no receipt and the seller cannot explain where the bike came from.
• The frame number does not match the number on the available papers.
• The lock is damaged or missing, or the seller has no matching key.
• The price is strikingly low for the make, model and condition of the bike.

A missing frame number, or one that has deliberately been made unreadable, is a serious warning sign. Do not buy such a bike unless its origin can be convincingly shown.

Status check clear, details consistent and you trust the seller? Then you can complete the purchase. Keep the frame number, the receipt, the advert and, if you have it, proof of payment. That puts you in a stronger position if you ever need to show where the bike came from.

Bought a bike? Register it in your name in the BIKEBAZE bike registry

The check does not stop at the purchase. By registering your new bike straight away, you keep the most important information safely in one place.

• Is the bike already registered with BIKEBAZE? Ask the previous owner to pass the registration to you through transfer of ownership.
• Is the bike not registered yet? Register it for free in your name. Add as many details as possible: frame number, make, model, colour, photos and proof of purchase.

You then have a digital ownership file with a PDF proof of ownership that, together with your receipt, is always at hand.

Why registering also helps you get your bike back

Registering is not just useful for your records. It also makes a difference if your bike is ever stolen. A registered bike is recognisable and linked to you. Anyone who finds or checks the bike sees the theft report and can send you an anonymous message and share the location through BIKEBAZE.

What does a SafeTag do against bike theft?

A SafeTag is an eye-catching, tamper-resistant anti-theft sticker with a unique scannable code. It is linked to your bike registration. A thief sees straight away that the bike is registered and recognisable. Anyone who comes across a suspicious bike can use the code to check its status in seconds.

From our production data from 2022 to 2026, bikes with a SafeTag are stolen 98% less often. If such a bike is stolen anyway, 27% come back to their owner, compared with 2 to 5% nationally.

The SafeTag is an optional addition to the free bike registration and costs €9.99 per set of two: a large tag for the frame and a small one for the battery. Combine it with a good lock and other precautions. Your bike is then not only better protected but also easier to recognise if someone finds it.

Why does your frame number stay important after the purchase?

The frame number stays useful when you have owned the bike for years:

• Police report and recovery: the police use details such as the frame number and chip number to identify a stolen bike. With these details you can file a more complete report, and a recovered bike is easier to link to you. You can report a theft without a frame number, but identification becomes harder.
• Insurance: many insurers ask for the frame number when you take out bike insurance or file a claim.
• Warranty and recalls: bike shops and manufacturers use identification details for warranty, recalls and sometimes to find the right parts.
• Ownership and transfer: a registration with frame number, photos and proof of purchase makes the bike's history clear. When you sell, you transfer the details to the new owner through BIKEBAZE.

Bike stolen? Report it to the police and to BIKEBAZE

If your bike is stolen, always report it to the police. The theft is then processed in the police registers and the bike becomes recognisable as stolen. The police can use the report to identify a recovered bike and investigate theft or handling of stolen goods. Residents can report some crimes, including theft, online with DigiD (the Dutch digital ID); the online form is in Dutch. Without DigiD, call 0900-8844 to make an appointment at a police station. Bring your ID.

Report your bike as stolen at BIKEBAZE. You can do this without an account and without a previous registration. From that moment, anyone who looks up the frame number or scans the SafeTag sees that your bike is stolen. A finder can reach you and share the location, all anonymously. A report at BIKEBAZE does not replace the police report: do both.

Keep and share as many details as possible with your report: the frame number, photos, receipt, make, model, colour, distinctive damage and, if you have one, a chip number or SafeTag ID. If your bike has vanished, also check whether the municipality removed it and took it to the fietsdepot (the municipal bike depot). Read the full step-by-step guide in Bike stolen? How to report it to the police and increase the chance of recovery.

How often are bikes stolen in the Netherlands?

Bike theft remains a big problem. According to CBS StatLine (Statistics Netherlands), the police registered 86,130 bike thefts in 2024 and 86,950 in 2025 (both provisional figures). Those are only the thefts that were reported. Estimates point to at least 750,000 to almost 1 million bike thefts a year in the Netherlands alone: the CBS Safety Monitor puts 2023 at 928,000 stolen bikes, and at 970,000 if you include bikes taken during a burglary or recovered later.

That is exactly why writing down the frame number, reporting the theft, a clear bike registration and visible recognisability matter. The more bikes are recognisable and the more often people check a suspicious bike, the harder it becomes to sell stolen bikes unnoticed.

Frequently asked questions about a bike's frame number

Can I register my bike without a frame number?

Yes. With BIKEBAZE you can record as many other details as possible, such as make, model, type, colour, photos and distinctive features. A frame number does matter for identifying the bike reliably. With a linked SafeTag ID, a bike without a readable frame number also gets a unique, scannable identifier. Always keep the purchase documents too, if you have them.

What does it cost to check a frame number and register my bike?

Checking a bike with Stop Heling, the RDW bicycle theft register and BIKEBAZE is free. Registering your bike with BIKEBAZE is free as well. If you want to make your registration visible on the bike, you can add a SafeTag for €9.99.

How do I make a hard-to-read frame number legible?

Clean the spot carefully with a soft cloth and, if needed, a little suitable degreaser. Then shine a torch or your phone's flash across the surface at an angle, so the stamped or engraved characters stand out. Looking from different angles often helps too. Do not scratch, sand or engrave anything yourself: you could damage the number.

Is a stolen bike always listed in Stop Heling, the RDW register or BIKEBAZE?

No. For Stop Heling and the RDW register, the listing depends on a police report and its processing. At BIKEBAZE, the owner can report the bike stolen themselves, even without an account. The BIKEBAZE status check also consults Stop Heling and Bike Index. No theft report found therefore does not guarantee the bike was not stolen.

Can I also check Stop Heling through BIKEBAZE?

Yes. When you look up a bike's status through BIKEBAZE, the BIKEBAZE bike registry, Stop Heling and Bike Index are consulted automatically. You do not have to run those checks one by one. If you also want to check the RDW bicycle theft register, you can do that directly at RDW.

What if a bike is already registered in someone else's name at BIKEBAZE?

Ask the seller to pass the registration to you through BIKEBAZE's transfer of ownership. Check that the frame number and the other details match. If the seller cannot make it plausible that the bike is really theirs, do not complete the purchase.

Can I check a frame number from outside the Netherlands?

Yes. Stop Heling, the RDW register and the BIKEBAZE bike check are public websites and work from anywhere. Stop Heling has an English version, and the BIKEBAZE check also consults Bike Index, an international bike registry. The RDW search page is in Dutch only.

Protect your bike with BIKEBAZE

Checking a frame number takes little effort and can save you a lot of trouble. It will not prevent every form of theft or handling of stolen goods, but it helps you judge whether a second-hand bike is safe to buy.

And after the purchase? With BIKEBAZE you can easily register your bike in your name, keep the important details together and make the bike quicker to recognise if it is ever stolen. Registration is completely free. If you also want to show that your bike is registered, add a SafeTag.

Check a bike with BIKEBAZE or register your bike for free. Together we make it harder to sell stolen bikes and increase the chance that bikes come back to their owners.