The Collaborative International Dictionary of English v.0.48:

Exaction \Ex*ac"tion\, n. [L. exactio: cf. F. exaction.]
   1. The act of demanding with authority, and compelling to pay
      or yield; compulsion to give or furnish; a levying by
      force; a driving to compliance; as, the exaction to
      tribute or of obedience; hence, extortion.
      [1913 Webster]

            Take away your exactions from my people. --Ezek.
                                                  xlv. 9.
      [1913 Webster]

            Daily new exactions are devised.      --Shak.
      [1913 Webster]

            Illegal exactions of sheriffs and officials.
                                                  --Bancroft.
      [1913 Webster]

   2. That which is exacted; a severe tribute; a fee, reward, or
      contribution, demanded or levied with severity or
      injustice. --Daniel.
      [1913 Webster]

WordNet (r) 3.0 (2006):

exaction
    n 1: act of demanding or levying by force or authority;
         "exaction of tribute"; "exaction of various dues and fees"

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "exaction":
   admission, admission fee, anchorage, blackmail, bother, brokerage,
   burdening, call, call for, carfare, cellarage, charge, charges,
   charging, claim, contribution, cover charge, demand, demand for,
   dockage, draft, drain, dues, duty, entrance fee, exactment,
   extortion, extortionate demand, fare, fee, freighting,
   heavy demand, hire, imposing an onus, imposition, impost,
   inconsiderateness, inconvenience, indent, infliction,
   insistent demand, laying on, levy, license fee, loading,
   loading down, nonnegotiable demand, notice, obtrusiveness, order,
   pilotage, portage, presumptuousness, rending, requirement,
   requisition, ripping, rush, rush order, salvage, scot,
   scot and lot, shot, storage, tasking, tax, taxing, tearing, toll,
   towage, tribute, trouble, ultimatum, unwarranted demand, warning,
   weighting, wharfage, wrench, wrenching, wrest, wresting, wring,
   wringing



Bouvier's Law Dictionary, Revised 6th Ed (1856):

EXACTION, torts. A willful wrong done by an officer, or by one who, under
color of his office, takes more fee or pay for his services than what the
law allows. Between extortion and exaction there is this difference; that in
the former case the officer extorts more than his due, when something is due
to him; in the latter, he exacts what is not his due, when there is nothing
due to him. Wishard; Co. Litt. 368.