Interest on Deficiencies and Delinquencies

# (1)

(1) Adjustment to statutory rate. For deficiencies and delinquencies owing on or after January 1, 2026, unless otherwise provided by law, every deficiency and delinquency arising under any law administered by the department will bear interest at the rate of eight percent annually. For historic interest rates, see section (4) of this rule.

# (2)

(2) Interest start date. The interest start date for deficiencies and delinquencies will be one day after the due date of the return, excluding extensions.

# (3)

(3) Interest periods.

(a) An interest period is one full calendar day beginning with the interest start date. Interest will be computed on a daily basis. The daily rate is based on a 365-day year.

(b) The daily interest rate is calculated by dividing the annual interest rate by 365 without rounding.

# (4)

(4) Interest rates. The following table shows interest rates used by the department to compute interest due from taxpayers on deficiencies and delinquencies.