1. (a) For purposes of this section, "final tax liability" has the meaning set forth in IC 6-3-4-4.2 (a)(1).

2. (b) The penalty at the rate prescribed by IC 6-8.1-10-2.1 (b) shall be assessed by the department on a taxpayer who fails to make payments as required in IC 6-5.5-6 . However, no penalty shall be assessed for a quarterly payment if the payment equals or exceeds:

   1. (1) twenty percent (20%) of the final tax liability for the taxable year; or
   2. (2) twenty-five percent (25%) of the final tax liability for the taxpayer's previous taxable year.

3. (c) The penalty for an underpayment of tax on a quarterly return shall only be assessed on the difference between the actual amount paid by the taxpayer on the quarterly return and the lesser of:

   1. (1) twenty percent (20%) of the taxpayer's final tax liability for the taxable year; or

   2. (2) twenty-five percent (25%) of the taxpayer's final tax liability for the taxpayer's previous taxable year.

      A payment required to be made in the manner prescribed in IC 6-5.5-6-3 (c), but not paid in such a prescribed manner, shall be subject to the penalty provided in IC 6-8.1-10-2.1 (b)(5).

4. (d) For a corporation required to make estimated payments under this section:

   1. (1) if a corporation has a current taxable year that is less than twelve (12) months, the amounts under subsections (b) and (c) shall be adjusted in the same manner as an estimated payment required under IC 6-3-4-4.2 ; and
   2. (2) any taxes withheld on behalf of the corporation under IC 6-3-4 or IC 6-5.5-2-8 , and any taxes remitted on behalf of the corporation under IC 6-3-2.1 , shall be treated as estimated tax payments on behalf of the corporation for purposes of this section. Such taxes shall be attributed to each required payment in the manner the underlying income is attributed under Section 6655 of the Internal Revenue Code.

As added by P.L.347-1989(ss), SEC.1. Amended by P.L.1-1991, SEC.55; P.L.159-2021, SEC.29; P.L.205-2025, SEC.14; P.L.128-2026, SEC.25.