Ind. Code § 6-8.1-10-1 – Liability for interest

(a) If a person fails to file a return for any of the listed taxes, fails to pay the full amount of tax shown on the person's return by the due date for the return or the payment, or incurs a deficiency upon a determination by the department, the person is subject to interest on the nonpayment.
(b) The interest for a failure described in subsection (a) is the adjusted rate established by the commissioner under subsection (c), from the due date for payment. The interest applies to:
1. (1) the full amount of the unpaid tax due if the person failed to file the return;
2. (2) the amount of the tax that is not paid, if the person filed the return but failed to pay the full amount of tax shown on the return; or
3. (3) the amount of the deficiency.
(c) The commissioner shall establish an adjusted rate of interest for a failure described in subsection (a) and for an excess tax payment on or before November 1 of each year. For purposes of subsection (b), the adjusted rate of interest shall be the percentage rounded to the nearest whole number that equals two (2) percentage points above the average investment yield on state general fund money for the state's previous fiscal year, excluding pension fund investments, as determined by the treasurer of state on or before October 1 of each year and reported to the commissioner. For purposes of IC 6-8.1-9-2 (c), the adjusted rate of interest for an excess tax payment must be the same as the adjusted rate of interest determined under this subsection for a failure described in subsection (a). The adjusted rates of interest established under this subsection shall take effect on January 1 of the immediately succeeding year.
(d) For purposes of this section, the filing of a substantially blank or unsigned return does not constitute a return.
(e) Except as provided by IC 6-8.1-3-17 (d), IC 6-8.1-3-17 (f), IC 6-8.1-5-2 , and section 2.1(k) of this chapter, the department may not waive the interest imposed under this section.
(f) Subsections (a) through (c) do not apply to a motor carrier fuel tax return.
As added by Acts 1980, P.L.61, SEC.1. Amended by P.L.60-1990, SEC.13; P.L.48-1994, SEC.3; P.L.2-1995, SEC.36; P.L.2-2005, SEC.23; P.L.236-2005, SEC.2; P.L.1-2006, SEC.147; P.L.211-2007, SEC.43; P.L.113-2014, SEC.13; P.L.214-2018(ss), SEC.14; P.L.234-2019, SEC.36; P.L.1-2025, SEC.105.