Indiana Code Title 6. Taxation § 6-4.1-4-2

Sec. 2. (a) If the Internal Revenue Service allows an extension on a federal estate tax return, the corresponding due date for the Indiana inheritance tax return is automatically extended for the same period as the federal extension.

(b) If the department of state revenue finds that because of an unavoidable delay an inheritance tax return cannot be filed before the deadline established by the appropriate probate court or the department of state revenue, the department of state revenue may extend the period for filing the return.  After the expiration of the first extension period, the department of state revenue may grant a subsequent extension if the person seeking the extension files a written petition that states the reason for the delay in filing the return.

(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.