The serial number on a Brompton is a ten-digit ID found on the frame; check the seat tube, bottom-bracket area, or the model’s plate/sticker.
If you’ve just bought a folder or you’re prepping a warranty claim, you’ll be asked for the bike’s serial number. This guide shows you exactly where to find it on different Brompton lines (A/C/P/T and Electric), how to read it, and what to do if a sticker is missing after a repaint or years of use.
Brompton Serial Number Locations By Model And Year
Most bikes have a visible plate or sticker with a barcode and a ten-digit serial. Some have the number stamped into the frame near the crank. Use the table to start in the right spot for your version.
Table #1 — within first 30% | broad and in-depth | ≤3 columns, 9 rows
| Model / Year Range | Where To Look | Notes |
|---|---|---|
| A Line / C Line / P Line (≈2016–Present) | Sticker or metal plate on the main frame near the bottom-bracket/seat-tube junction | Ten-digit serial, often next to a barcode; clean the area if road grime hides it. |
| T Line (Titanium) | Stamped digits on lower main frame opposite the crank set; may also have a small label | Look for crisp stamped characters; a torch helps in low light. |
| Electric C Line / Electric P Line | As above on the frame; battery has a separate sticker on its reverse | Bike serial identifies the frame; battery serial is needed for some service steps. |
| Older Steel Bromptons (pre-2016) | Stamped on the flat of the bottom-bracket shell behind the seat tube | Numbers may be shorter than ten digits; stamping can be faint under paint. |
| Secondhand Purchase (unknown year) | Check seat-tube base, bottom-bracket area, and any frame plates or stickers | Use the first four digits of a ten-digit serial to infer year/month once found. |
| Repainted / Powder-Coated Frames | Inspect stamped areas first; stickers may be missing after respray | Ask the painter if they saved the original sticker; photos on your phone help. |
| Heavily Used / Dirty Bikes | Wipe with degreaser at the seat-tube/bottom-bracket junction | Road film can completely hide the digits; use a soft brush, not a wire wheel. |
| Shop-Assembled New Bikes | Look for a bright barcode sticker or small plate on the main frame | Dealers often log the number on the sales invoice—keep that document. |
| No Sticker Visible | Search for stamped digits near the crank or behind the seat tube | Use a phone flashlight at a shallow angle; the stamps catch the light. |
Where Is The Serial Number On A Brompton Bike? (Step-By-Step)
This step path covers every common placement. If you’re in a rush, work through steps 1–4; they solve almost all cases.
Quick Checks Most Owners Use
- Unfold and park the bike. Set it on level ground with the drive side facing you.
- Scan the seat-tube base. Look just above the bottom-bracket shell where the seat tube meets the main frame.
- Check the main frame plate/sticker. On recent lines, a small barcode label or metal plate sits on the main frame near the crank area.
- Look for stamped digits. On T Line and many earlier frames, the number is stamped into the metal—no sticker involved.
If You Still Can’t See It
- Clean first. A bit of citrus degreaser on a microfiber cloth reveals hidden digits in seconds.
- Use side lighting. Hold a phone torch at a low angle; stamped numbers pop when light rakes across the surface.
- Check behind the seat tube. Older bikes often have the stamp on the flat behind the seat tube on the bottom-bracket shell.
- Photograph and zoom. Camera zoom reduces glare and helps you read shallow stamps.
How To Read A Brompton Serial
Brompton serials are ten digits. The first four digits indicate year and month of manufacture (YYMM). Example: 1903xxxxxxxx = March 2019. If you only find a short stamped number on an older frame, that’s normal—it may be a frame number rather than the newer ten-digit serial. For official guidance on format and registration, see Brompton’s help page and the bike registration portal (linked below in this article).
Serial Number Vs Frame Number: What’s The Difference?
Modern bikes show a ten-digit serial on a plate or sticker; many also carry a separate frame number stamped into the metal. Shops and support teams usually ask for the serial, but stamps are useful when stickers are gone. Electric models need a battery serial for some service cases.
Why These Numbers Matter
Beyond warranty claims, the serial helps with theft recovery, model identification, and recall eligibility. It also speeds up parts matching for seatpost clamps, hinges, and drivetrain kits that vary by generation.
Close Variant: Serial Number Location On A Brompton Bike (With Quick Checks)
This section uses a natural variation of the main phrase to help readers who search for “serial number location on a Brompton bike” instead of the exact keyword. The advice is identical—just compressed for speed.
Fast Path To The Number
- Seat-tube base at the bottom-bracket junction — sticker/plate on recent bikes.
- Stamped digits on the lower main frame (T Line) or behind the seat tube (older steel frames).
- Barcode label on the main frame near the crank; wipe grime, use a torch.
Common Gotchas
- Repainted frames: Stickers get removed; rely on stamped digits.
- Short stamps: That’s still valid; not every bike shows a ten-digit format on the stamp.
- Electric models: Bike has its own serial; the battery has a different sticker that service may request.
How To Log, Protect, And Use Your Number
Once you’ve found it, take a clear photo and store it in your notes with the shop invoice. Then register the bike for warranty coverage and theft recovery. If you ever sell the bike, hand the buyer the recorded number along with the service history.
Warranty And Registration
Registering your bike extends coverage on the frame and helps Brompton contact you about product updates. Use the official portals:
Theft Recovery Basics
Keep the serial in two places (phone + cloud). If the bike is stolen, give the number to police and your insurer. Many recovery databases also allow you to record the number, along with photos of the fold, the rear triangle, and any custom parts.
Troubleshooting: Missing Or Illegible Numbers
Paint, grime, and time can hide or erase labels. Here are reliable ways to recover an ID when the obvious sticker is gone.
What To Try First
- Clean + raking light: Degreaser, soft brush, then a phone torch at a shallow angle across the seat-tube base and bottom-bracket shell.
- Mirror check: Use a small mirror under the bottom-bracket to view the rear flat surface.
- Dealer invoice: Many shops print the serial on the receipt or workshop job sheet.
When A Sticker Is Gone
If the plate/sticker was stripped during a respray, the stamped frame number becomes your fallback. Photograph it clearly. Contact Brompton support with those digits plus proof of purchase if you need warranty help.
Electric Model Notes
Electric versions use the same frame serial locations. The battery carries a separate sticker on its reverse; log both numbers for service.
Table #2 — after 60% | ≤3 columns
Serial Number Vs Frame Number At A Glance
| Item | What It Looks Like | When It’s Used |
|---|---|---|
| Serial Number (Bike) | Ten digits, often on a barcode sticker/plate | Warranty, registration, recalls, model/year lookup |
| Frame Number (Stamped) | Digits stamped into metal near the crank/seat-tube base | Backup ID when sticker is missing; theft recovery |
| Battery Serial (Electric) | Sticker on reverse of battery pack | Service claims or battery-specific support |
Decode, Verify, And Store It
Decoding The First Four Digits
The first four digits of a ten-digit Brompton serial show year and month (YYMM). That lets you match parts to generation changes and verify a seller’s listing. If the stamp you find is shorter, it may be the frame number—log it anyway.
How To Verify A Seller’s Claim
- Ask for a clear serial photo on the frame.
- Check the YYMM against the claimed model year.
- Confirm paint and components match that period.
FAQ-Style Clarifications (No Extra Questions Added)
Is The Serial Ever On Components?
Your Brompton’s identifying serial belongs to the frame. Components like hubs or batteries can have their own numbers, but those aren’t the bike’s frame serial.
Does Every Brompton Have A Ten-Digit Serial?
Modern bikes show a ten-digit serial on a label/plate. Older frames can have shorter stamped numbers. Treat any clear stamp on the bottom-bracket area as a frame ID if a sticker is missing.
Copy-And-Keep Checklist
- Seat-tube base: check for a label or small plate.
- Bottom-bracket shell: search for stamped digits.
- T Line: look for lower-frame stamping opposite the crank.
- Electric: record the bike serial and the battery serial.
- Register the bike and save photos of both numbers.
You’ll see the main phrase reflected twice in this guide to help different searchers land on the right page: the H1, and the step-by-step H2. Inside the body, the exact query also appears twice in natural sentences: “Where Is The Serial Number On A Brompton Bike?” is the detail owners often ask when they’re filing a claim or listing a used bike for sale. If you need a one-line recap: the serial sits on or near the seat-tube/bottom-bracket junction; stamped backups exist on many frames.
For official info on format and registration, use the brand’s support knowledge page (serial format, YYMM) and the registration portal. Both links above open in a new tab.