Ind. Code § 6-4.1-4-2
(c) For purposes of sections 3 and 6 of this chapter, an inheritance tax return is not due until the last day of any extension period or periods granted under this section.
As added by Acts 1976, P.L.18, SEC.1. Amended by P.L.252-2001, SEC.3; P.L.238-2005, SEC.2; P.L.190-2016, SEC.3; P.L.79-2017, SEC.18.