Reference

Motorcycle and trailer VINs

Motorcycles, trailers, low-speed vehicles and incomplete vehicles use the same seventeen-character VIN as cars, under the same federal rule. Here is what changes for each type, how small builders identify themselves, and why some trailers have no standard VIN at all.

By Pixoware. Published 26 October 2026.

The short answer

A motorcycle or trailer built for road use carries the same kind of VIN as a car: seventeen characters, a check digit in position 9, and the same four sections. What changes is what the middle section must describe, and two small rules that only bind cars and light trucks. A builder that makes fewer than 1,000 vehicles of a type a year uses a six-character manufacturer identifier, signalled by a 9 in position 3. A trailer built at home, or before the 17-character format began, may have no standard VIN at all.

This guide builds on how to read a VIN, which covers all seventeen positions.

Same seventeen characters, same rules

The federal VIN rule, 49 CFR Part 565, treats passenger cars, multipurpose passenger vehicles, trucks, buses, trailers, incomplete vehicles, low-speed vehicles and motorcycles as separate types and applies one format to all of them. Under 565.13 every VIN has seventeen characters with no blanks, never uses I, O or Q, and must appear clearly and indelibly on a part not designed to be removed except for repair, or on a label permanently fixed to one. No two vehicles built within 60 years starting with the 1980 model year may share a VIN.

Part 565 borrows its definitions from 49 CFR 571.3. A motorcycle has a seat or saddle for the rider and is designed to travel on no more than three wheels. A trailer is designed to carry people or property and to be drawn by another motor vehicle.

Two rules in 565.15 apply only to passenger cars and to multipurpose vehicles and trucks of 10,000 lb GVWR or less:

Position 7 need not be a letter. On a car, a letter there places the year code in position 10 in the 2010 to 2039 cycle. On a motorcycle or trailer that test does not apply, so a year code can point to two years 30 apart. Our check digit page uses the position 7 test for its year hint, so treat that hint as a guess here. The decoder shows the model year vPIC returns.
Four digits at the end, not five. Cars and light trucks must end in five digits. Every other vehicle, motorcycles and trailers included, must end in four.

The check digit works the same on every type; see how the check digit works.

What positions 4 to 8 must describe

Positions 4 to 8 are the vehicle descriptor section. The manufacturer picks the characters, but Table I of 565.15 lists the attributes that must be decipherable from them, using the decoding key the manufacturer files with NHTSA.

Motorcycles

Make, type of motorcycle, line, engine type and net brake horsepower. The horsepower coded must be within 10 percent of the actual figure. For a motorcycle of 2 horsepower or less it may differ by no more than 2, and above that it must be greater than 2. NHTSA's handbook for new manufacturers says this keeps the distinction between a motorcycle and a motor-driven cycle, which 571.3 defines as a motorcycle with 5 brake horsepower or less.

Trailers

Make, type of trailer, body type, length and axle configuration. The same row covers trailer kits, meaning trailers delivered complete but unassembled, and incomplete trailers. NHTSA's handbook gives a sample layout: connection type (ball, gooseneck or bumper pull) in position 4, body type in position 5, length in feet in positions 6 and 7, and number of axles in position 8. It is an example, not a requirement. When NHTSA updated Part 565 in 2008 it declined to exempt trailers from coding the make, noting that a maker with 33 or fewer combinations of the required attributes could express them in one character.

Low-speed vehicles

A low-speed vehicle has four wheels, a GVWR under 3,000 lb, and a top speed above 20 mph but no more than 25 mph on a paved level surface. Its VIN must describe the make, engine type, brake system, restraint system type, body type and GVWR. The 2008 rule dropped these vehicles from the position 7 letter requirement, so they are treated like trailers and motorcycles there.

Incomplete vehicles

An incomplete vehicle is at least a frame and chassis with power train, steering, suspension and brakes that needs more than minor finishing to be complete. Unless it is a trailer, its VIN must describe the make, model or line, series, cab type, engine type and brake system. An incomplete trailer uses the trailer row. Under 565.13 a vehicle built in stages keeps the VIN its incomplete vehicle manufacturer assigned, so a decode can describe the chassis rather than the finished body.

Small builders and the six-character identifier

Part 565 counts a manufacturer that builds fewer than 1,000 vehicles of a given type each year as low-volume. Such a maker identifies itself with six characters: positions 1 to 3 plus positions 12 to 14. The regulation says a 9 in position 3 always indicates a six-character identifier. That leaves positions 15 to 17 for the production number, and because motorcycles and trailers must end in four digits, position 14 must be a digit too.

The paperwork is the same as for a large maker. Under 565.16, a US maker gets its identifier from SAE International at no charge and must submit it at least 60 days before affixing the first VIN that uses it, and the decoding key is due at least 60 days before the first vehicle is offered for sale. Part 566 also requires a description of what the company builds within 30 days of starting manufacture, and a trailer maker must state the intended use, such as a tank trailer. NHTSA's vPIC database accepts six-character identifiers in its manufacturer lookup. For examples, see WMI codes explained.

Where the VIN is on these vehicles

A motorcycle's VIN is on its certification label, near where the steering post meets the handlebars; NHTSA's handbook notes that this label is the only place on a motorcycle that must show it. A trailer's label, with the VIN, goes on the forward half of the left side. A low-speed vehicle follows the car rule and shows its VIN through the windshield. For engine numbers, multistage labels and missing plates, see where to find the VIN.

Why a homemade or very old trailer may have no standard VIN

Part 565 makes the manufacturer responsible for the VIN, and a 1991 NHTSA interpretation letter put it plainly: the only person that can assign a VIN to a vehicle is the vehicle's manufacturer. The system relies on an identifier from SAE and a decoding key filed with NHTSA. A trailer welded together in a garage usually has neither, so even if it carries a number, a decoder has nothing to match it against.

Putting such a trailer on the road is a state matter. In a 1993 letter about kit cars and homemade cars, NHTSA said registration, inspection and operation of motor vehicles is a state function, and that a homemade car must meet the requirements of the state where it is licensed. Our advice: ask your state's DMV how it titles and numbers a homemade trailer before you build or buy one.

Age matters too. NHTSA's 1978 rule required a 17-character VIN from the 1981 model year. Before that, NHTSA says, VINs came in a wide array of configurations depending on the manufacturer, so an older trailer or motorcycle may carry a shorter number that will not pass a 17-character check. See why a VIN won't decode for other causes.

What RunThatVIN shows for a motorcycle or trailer

When you decode a VIN here, a motorcycle or trailer gets the same layout as a car: powertrain, body and manufacturing rows, a breakdown of the VIN's sections, and recall campaigns for the year, make and model. The vehicle type row shows the type vPIC returns, and empty rows say “Not provided” with a note on why.

Two limits. vPIC defines fields for trailer connection type, body type and length, and for motorcycle custom type, suspension and chassis type, but our decoder does not display them at present. And our breakdown always splits the VIN at the standard boundaries, so for a VIN with a 9 in position 3, the unit number it shows begins with the three characters that belong to the manufacturer identifier. The manufacturer row itself comes from vPIC.

Quick answers

Do motorcycles and trailers have 17-character VINs?

Yes. Federal rules in 49 CFR Part 565 give motorcycles, trailers, low-speed vehicles and incomplete vehicles the same 17-character format as cars, with a check digit in position 9. Vehicles built before the 1981 model year may have shorter numbers.

What does a 9 in the third position of a trailer VIN mean?

It means the manufacturer builds fewer than 1,000 vehicles of that type a year. Its identifier is six characters, positions 1 to 3 plus positions 12 to 14, and only positions 15 to 17 are the production number.

What must a trailer VIN describe?

Positions 4 to 8 must encode the make, type of trailer, body type, length and axle configuration. Each manufacturer chooses its own codes and files the key with NHTSA.

Why won't my homemade trailer's number decode?

A VIN decoder reads numbers assigned by manufacturers that registered an identifier and filed decoding information with NHTSA. A homemade trailer usually has neither. Registration is handled by the states, so ask your state's DMV how it numbers and titles homemade trailers.

Sources

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