They do, Needs to be posted on the truck some where. Although if it is missing or not complete they won't (in most cases) have a problem with it.
No need to mark your vehicle with a unit number; however, if a unit number is available it has to be marked on the maintenance file. http://www.fmcsa.dot.gov/rules-regu.../fmcsrruletext.aspx?chunkKey=0901633480023979 Be safe.