John thanks for the link. On page 3 the last paragraph under who needs a DOT number it says WHEN YOU REG. YOUR VEHICLE IF YOU CANNOT PRODUCE A NUMBER YOUR APPILICATION WILL NOT BE PROSSESED. I reg. both the truck and the trailer at the same time and no one asked any ?. I also was telling my son about this and he said the state patrol stoped him and told him he needed the DOT number, so he got one and he started getting all kinds of letters with forms to fill out. He found out later that he didn't need a DOT number anyway. He has the same size rig as I have and also lives in Wi. We both only haul our own things and never for hire.