Indiana Code Title 29. Probate § 29-1-2-13

Sec. 13. (a) The intestate share or other expectancy to which the spouse or any other heir is entitled may be waived at any time by a written contract, agreement or waiver signed by the party waiving such share or expectancy.  The promise of marriage, in the absence of fraud, is sufficient consideration in the case of an agreement made before marriage.  In all other cases such contract, an agreement or waiver is binding upon the parties to the agreement if executed after a full disclosure of the nature and extent of such right, and if the thing or promise given to such party is a fair consideration under all the circumstances.

(b) Except as otherwise provided in the agreement, a waiver executed by the decedent's spouse is considered a waiver of the right to elect to take against the decedent's will.  The written agreement may be filed in the same manner as is provided for the filing of an election under IC 29-1-3-3.