My Cambridge Advanced Learner's Dictionary has 2 definitions (both verbs)
1.) [FORCE] to officially force a rule, tax, punishment to be obeyed or received.
2.) [EXPECT] to expect someone to do something for you ... they do not want to do.
so 1.) could be "A tax imposed for collection." or "To impose a tax for environmental reasons." and
2.) would almost always be "May I impose on you?" Can't think of ANY exceptions.