77.60 (1) (b) 2. Taxes refunded as a result of a field audit shall bear interest at the rate of 6 percent per year from the unextended due date of the taxpayer’s income or franchise tax return for that calendar or fiscal year or, if the filing of an income or franchise tax return under ch. 71 is not required, from the 15th day of the 4th month of the year after the close of the calendar or fiscal year to the date on which the refund is certified on the refund rolls.

AB1089,33 Section 33. 77.96 (5) of the statutes is amended to read:

77.96 (5) Each person subject to a surcharge under s. 77.93 shall, on or before the due date, including extensions, for filing under ch. 71, file an accurate statement of its gross tax liability. Payments made after the due date under sub. (2) and on or before the due date under this subsection are not delinquent but are subject to interest at the rate of 12 6 percent per year.

AB1089,34 Section 34. 78.68 (1) of the statutes is amended to read:

78.68 (1) Unpaid taxes shall bear interest at the rate of 12 6 percent per year from the due date of the tax until paid or deposited with the department, and all refunded taxes bear interest at the rate of 3 6 percent per year from the due date of the return to the date on which the refund is certified on the refund rolls.

AB1089,35 Section 35. 139.25 (1) of the statutes is amended to read:

139.25 (1) Interest and penalties. Unpaid taxes bear interest at the rate of 12 6 percent per year from the due date of the return until paid or deposited with the department, and all refunded taxes bear interest at the rate of 3 6 percent per year from the due date of the return to the date on which the refund is certified on the refund rolls.

AB1089,36 Section 36. 139.44 (9) of the statutes is amended to read:

139.44 (9) Unpaid taxes bear interest at the rate of 12 6 percent per year from the due date of the return until paid or deposited with the department, and all refunded taxes bear interest at the rate of 3 6 percent per year from the due date of the return to the date on which the refund is certified on the refund rolls.

AB1089,37 Section 37. 168.12 (6) (c) of the statutes is amended to read:

168.12 (6) (c) The department of revenue shall investigate the correctness and veracity of the representations in the claim and may require a claimant to submit records to substantiate the claim. The department of revenue shall either allow or deny a claim under this subsection not later than 60 days after the filing of the claim. If the department of revenue allows the claim, it shall pay the claimant the amount allowed from the moneys appropriated under s. 20.855 (4) (r). If the department of revenue does not pay the allowance by the 90th day after the date on which the purchaser files the claim, the department of revenue shall also pay interest on the unpaid claim beginning on that day, at the rate of 3 6 percent per year, from the moneys appropriated under s. 20.855 (4) (r).

AB1089,38 Section 38. 168.12 (6) (d) 2. of the statutes is amended to read:

168.12 (6) (d) 2. If the department of revenue has paid the claim, require the purchaser to refund to the department of revenue that portion of the amount paid under par. (c) to which the purchaser is not entitled and impose a penalty on the purchaser equal to 25 percent of the allowance, plus interest on the sum of the unpaid penalty and the amount required to be refunded, accruing from the date that the penalty is imposed, at the rate of 12 6 percent per year.

AB1089,39 Section 39. 168.12 (6) (e) 1. of the statutes is amended to read:

168.12 (6) (e) 1. If the claim has not been paid and the department of revenue allows no portion of the claim, impose a penalty on the purchaser equal to 50 percent of the amount claimed by the purchaser, plus interest on the unpaid penalty, accruing from the date that the penalty is imposed, at the rate of 12 6 percent per year.

AB1089,40 Section 40. 168.12 (6) (e) 3. of the statutes is amended to read:

168.12 (6) (e) 3. If the claim has been paid, require the purchaser to refund to the department of revenue that portion of the amount paid under par. (c) that the department of revenue determines was fraudulently obtained and impose a penalty on the purchaser equal to 50 percent of the amount claimed by the purchaser, plus interest on the sum of the unpaid penalty and the amount required to be refunded, accruing from the date that the penalty is imposed, at the rate of 12 6 percent per year.

AB1089,41 Section 41. Initial applicability.

(1) Interest on underpayments and overpayments. This act first applies to assessments issued and refunds paid on December 31, 2024, regardless of the taxable periods to which the assessments or refunds pertain.