Alteration of Instrument Law and Legal Definition

Alteration of instrument is a change in the sense or language of the instrument effected by an intentional act performed on the instrument by a party entitled to the instrument.

An alteration of an instrument is material when it destroys the identity of the instrument, or results in different legal obligations than those originally binding upon the parties to the instrument. A material alteration vitiates the instrument, unless it was done by express or implied consent. [United States v. Reinking, 172 F. Supp. 131 (D. Mo. 1958)].