Indiana Code Title 6. Taxation § 6-5.5-6-2

Sec. 2. (a) Annual returns required by this chapter shall be filed with the department on or before the fifteenth day of the fifth month following the close of the taxpayer's taxable year.

(b) If the due date for a federal income tax return is extended by the Internal Revenue Service to a date that is later than the date specified in subsection (a), the department may extend the due date of a return required to be made under this chapter to reflect the due date permitted for the federal income tax return.

(c) If the due date for a federal income tax return in the Internal Revenue Code, as determined without regard to any extensions, Saturdays, Sundays, or holidays, is later than the date provided in subsection (a), the due date for the return made pursuant to this section shall be the later of the due date for the federal income tax return or the due date provided under this section.