The Vehicle Identification Number (VIN) acts like your  car's unique code.  The VIN for heavy-duty trucks can be located in a few different places, as shown in the image.

You can also find it on your  vehicle insurance card or the title paperwork you received from the pertinent government department.

1 Driver's side sun visor
2 Driver's side door frame
3 Inside the glove box
4 Driver's side front frame rail