The vehicle identification number of a trailer and any commercial motor vehicle manufactured since June 1976 is usually printed on a paper sticker inside the vehicle. This is called the vehicle plate, and it includes the VIN and other important information about the trailer. The VIN is comprised of 17 characters and is labeled as the manufacturer's serial number. Note that the VIN is different from the model number.
If there is no data plate inside the trailer, check the trailer tongue, which is a series of front steel beams at the front of the trailer to which the tow hitch is attached. Check behind the skirting at the front of the metal bars to find the I-beam. The VIN is most likely stamped horizontally or vertically into the metal. The VIN may also be located on the trailer's frame, at the rear end, near the axle and on any primary frame members of the vehicle.
The VIN of many older trailers is difficult to verify at the time of inspection. In this case, the new owner of the trailer can request a new VIN at the Department of Motor Vehicles. The purchaser must show a valid title or proof of ownership and a bill of sale. Once the DMV inspector deems that the trailer's VIN is illegible or missing, the owner must complete an affidavit and submit it to the DMV for a reassignment of the VIN.