70.38 (1m) Estimated liability. Upon written request and for sufficient reason shown, the department shall allow a person subject to the tax under s. 70.375 to file, on or before June 15, a net proceeds tax return and to pay that tax based upon estimated tax liability. On or before September 15, that person shall file a final report and pay any additional tax due along with interest at the rate of 1 0.5 percent per month from June 15 until the date of payment. If the additional tax exceeds 10 percent of the person’s tax under s. 70.375 for the previous year, the penalty and interest under s. 70.39 (1) apply. If the final report indicates that the person overpaid the person’s liability, the department shall refund the overpayment.

71.03 (7) Extension of time to file. (intro.) Returns of natural persons and fiduciaries that require a statement of amounts or information contained or entered on a corresponding return under the internal revenue code shall be filed within the time fixed under that code for filing of the corresponding federal return. Any extension of time granted by law or by the internal revenue service for the filing of that corresponding federal return extends the time for filing under this chapter if a copy of the taxpayer’s application to the internal revenue service requesting the extension is filed with the return under this chapter or if a copy of any request for an extension required by the internal revenue service is filed with the return under this chapter or at an earlier date that the department prescribes by rule and if the taxpayer pays the Wisconsin tax in the manner applicable to federal income taxes under the internal revenue code. Taxes payable upon the filing of the return do not become delinquent during the period of an extension but are subject to interest at the rate of 12 6 percent per year during such period except as follows:

71.24 (7) (a) In the case of a corporation required to file a return, the department of revenue shall allow an automatic extension of 7 months or until the original due date of the corporation’s corresponding federal return, whichever is later. Any extension of time granted by law or by the internal revenue service for the filing of corresponding federal returns shall extend the time for filing under this subchapter to 30 days after the federal due date if the corporation reports the extension in the manner specified by the department on the return. Except for payments of estimated taxes, income or franchise taxes payable upon the filing of the tax return shall not become delinquent during such extension period, but shall, except as provided in par. (b), be subject to interest at the rate of 12 6 percent per year during such period.

71.44 (3) (a) In the case of a corporation required to file a return, the department of revenue shall allow an automatic extension of 7 months or until the original due date of the corporation’s corresponding federal return, whichever is later. Any extension of time granted by law or by the internal revenue service for the filing of corresponding federal returns shall extend the time for filing under this subchapter to 30 days after the federal due date if the corporation reports the extension in the manner specified by the department on the return. Except for payments of estimated taxes, income or franchise taxes payable upon the filing of the tax return shall not become delinquent during such extension period, but shall, except as provided in par. (b), be subject to interest at the rate of 12 6 percent per year during such period.

71.775 (4) (bm) 1. For the return under par. (a), the department shall allow an automatic extension of 7 months or until the corresponding due date of the pass-through entity’s federal income tax return or return of partnership income, whichever is later. Except for payments of estimated taxes, and except as provided in subd. 2., withholding taxes payable upon filing the return are not delinquent during the extension period but shall be subject to interest at the rate of 12 6 percent per year during that period.

71.775 (4) (bm) 2. For taxable years beginning after December 31, 2008, for persons who qualify for a federal extension of time to file under 26 USC 7508A due to a presidentially declared disaster or terroristic or military action, withholding taxes that are otherwise due from a pass-through entity under sub. (2) are not subject to 12 6 percent interest as otherwise provided under subd. 1. during the extension period and for 30 days after the end of the federal extension period.

71.775 (4) (em) Except as provided in par. (fm), in the case of any underpayment of estimated withholding taxes under par. (cm), interest shall be added to the aggregate withholding tax for the taxable year at the rate of 12 6 percent per year on the amount of the underpayment for the period of the underpayment. In this paragraph, “period of the underpayment” means the time period beginning with the due date of the installment and ending on either the unextended due date of the return under par. (a) or the date of payment, whichever is earlier. If 90 percent of the tax due under sub. (2) for the taxable year is not paid by the unextended due date of the return under par. (a), the difference between that amount and the estimated taxes paid, along with any interest due, shall accrue delinquent interest in the same manner as income and franchise taxes under s. 71.82 (2) (a).

71.82 (1) Normal. (a) In assessing taxes interest shall be added to such taxes at 12 6 percent per year from the date on which such taxes if originally assessed would have become delinquent if unpaid, to the date on which such taxes when subsequently assessed will become delinquent if unpaid.

(b) Except as otherwise specifically provided, in crediting overpayments of income and surtaxes against underpayments or against taxes to be subsequently collected and in certifying refunds of such taxes interest shall be added at the rate of 3 6 percent per year from the date on which such taxes when assessed would have become delinquent if unpaid to the date on which such overpayment was certified for refund except that if any overpayment of tax is certified for refund within 90 days after the last date prescribed for filing the return of such tax or 90 days after the date of actual filing of the return of such tax, whichever occurs later, no interest shall be allowed on such overpayment. For purposes of this section the return of such tax shall not be deemed actually filed by an employee unless and until the employee has included the written statement required to be filed under s. 71.65 (1). However when any part of a tax paid on an estimate of income, whether paid in connection with a tentative return or not, is refunded or credited to a taxpayer, such refund or credit shall not draw interest.

(c) Any assessment made as a result of the adjustment or disallowance of a claim for credit under s. 71.07, 71.28 or 71.47 or subch. VIII or IX, except as provided in sub. (2) (c), shall bear interest at 12 6 percent per year from the due date of the claim.

71.82 (2) (b) Department may reduce delinquent interest. The department shall provide by rule for reduction of interest under par. (a) to 12 6 percent per year in stated instances wherein the secretary of revenue determines that reduction is fair and equitable.

71.82 (2) (d) Withholding tax. Of the amounts required to be withheld any amount not deposited or paid over to the department within the time required shall be deemed delinquent and deposit reports or withholding reports filed after the due date shall be deemed late. Delinquent deposits or payments shall bear interest at the rate of 1.5 percent per month from the date deposits or payments are required under this section until deposited or paid over to the department. The department shall provide by rule for reduction of interest on delinquent deposits to 12 6 percent per year in stated instances wherein the secretary of revenue determines reduction fair and equitable. In the case of a timely filed deposit or withholding report, withheld taxes shall become delinquent if not deposited or paid over on or before the due date of the report. In the case of no report filed or a report filed late, withheld taxes shall become delinquent if not deposited or paid over by the due date of the report. In the case of an assessment under s. 71.83 (1) (b) 2., the amount assessed shall become delinquent if not paid on or before the first day of the calendar month following the calendar month in which the assessment becomes final, but if the assessment is contested before the tax appeals commission or in the courts, it shall become delinquent on the 30th day following the date on which the order or judgment representing final determination becomes final.

71.84 (1) Individuals and fiduciaries. Except as provided in s. 71.09 (11), in the case of any underpayment of estimated tax by an individual, estate or trust, except as provided under s. 71.09, there shall be added to the aggregate tax for the taxable year interest at the rate of 12 6 percent per year on the amount of the underpayment for the period of the underpayment. In this subsection, “the period of the underpayment” means the time period from the due date of the installment until either the 15th day of the 4th month beginning after the end of the taxable year or the date of payment, whichever is earlier.

71.84 (2) (a) Except as provided in s. 71.29 (7), in the case of any underpayment of estimated tax by a corporation under s. 71.29 or 71.48, there shall be added to the aggregate tax for the taxable year interest at the rate of 12 6 percent per year on the amount of the underpayment for the period of the underpayment. In this paragraph, “period of the underpayment” means the time period from the due date of the installment until either the date on which the corporation is required to file for federal income tax purposes, not including any extension, under the Internal Revenue Code or the date of payment, whichever is earlier. If 90 percent of the tax shown on the return is not paid by the date on which the corporation is required to file for federal income tax purposes, not including any extension, under the Internal Revenue Code, the difference between that amount and the estimated taxes paid, along with any interest due, shall accrue delinquent interest under s. 71.91 (1) (a).

71.84 (2) (b) For corporations that are subject to a tax under this chapter on unrelated business taxable income, as defined under section 512 of the internal revenue code, and virtually exempt entities, “period of the underpayment” means the time period from the due date of the installment until either the 15th day of the 5th month beginning after the end of the taxable year or the date of payment, whichever is earlier. If 90 percent of the tax shown on the return is not paid by the 15th day of the 5th month following the close of the taxable year, the difference between that amount and the estimated taxes paid along with any interest due, shall accrue delinquent interest under s. 71.91 (1) (a).