WordNet (r) 3.0 (2006):

tax collector
    n 1: someone who collects taxes for the government [syn: tax
         collector, taxman, exciseman, collector of internal
         revenue, internal revenue agent]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "tax collector":
   Internal Revenue Service, accumulator, assessor, bill collector,
   collection agent, collector, connoisseur, customhouse, customs,
   douanier, dunner, exciseman, farmer, gatherer, magpie, miser,
   pack rat, publican, revenuer, tax assessor, tax farmer, taxer,
   taxman