The Collaborative International Dictionary of English v.0.48:

Acquittance \Ac*quit"tance\, v. t.
   To acquit. [Obs.] --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Acquittance \Ac*quit"tance\, n. [OF. aquitance, fr. aquiter. See
   Acquit.]
   1. The clearing off of debt or obligation; a release or
      discharge from debt or other liability.
      [1913 Webster]

   2. A writing which is evidence of a discharge; a receipt in
      full, which bars a further demand.
      [1913 Webster]

            You can produce acquittances
            For such a sum, from special officers. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

acquittance
    n 1: a legal document evidencing the discharge of a debt or
         obligation [syn: acquittance, release]

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

ACQUITTANCE, contracts. An agreement in writing to discharge a party from an
engagement to pay a sum of money. It is evidence of payment. It differs from
a release in this, that the latter must be under seal, while an acquittance
need not be under seal. Poth. Oblig. n. 781. In Pennsylvania, a receipt,
(q.v.) though not under seal, has nearly the same effect as a release. 1
Rawle, R. 391. Vide 3 Salk. 298, pl. 2; Off. of Ex. 217 ; Co. Litt. 212 a,
273 a.