71.08(2) (2) Joint liability. If the requirements under sub. (1) are applicable and the spouses file a joint income tax return, they shall file a joint minimum tax return and are jointly and severally liable for the tax imposed under sub. (1) and for the interest, penalties, fees, additions to tax and additional assessments with respect to the tax.

71.08(3) (3) Administration. The department of revenue shall have full power to impose, enforce and collect the minimum tax provided in this section and may take any action, conduct any proceeding and in all respects proceed as it is authorized in respect to income taxes imposed in this chapter. The income tax provisions in this chapter relating to assessments, refunds, appeals, collection, interest and penalties shall apply to the minimum tax.

71.08(4) (4) Tax benefit rule. The department of revenue shall promulgate rules to provide that the amount under sub. (1) may be reduced to prevent the inclusion of any amounts, except the federal standard deductions, itemized deductions and personal exemptions, that do not reflect a benefit in respect to the tax imposed under s. 71.02.

71.09(1) (1) Definitions. In this section:

71.09(1)(a) (a) "Farmers or fishers" are individuals, estates or trusts whose estimated gross income from farming or fishing for the taxable year is at least two-thirds of the total estimated gross income from all sources for the taxable year or individuals, estates or trusts whose gross income from farming or fishing for the preceding taxable year was at least two-thirds of the total gross income from all sources shown on that return. If a person files a joint return, the income of both that person and that person's spouse shall be considered in determining whether the person is a farmer or fisher.

71.09(1)(b) (b) "Tax shown on the return" and "tax for the taxable year" mean the net tax imposed under s. 71.02 after reduction for exemptions to, and credits against, that tax but before reduction by amounts withheld under subch. X and before reduction for amounts paid as estimated tax under this section for that tax plus the tax imposed under s. 71.08 before reduction for amounts paid as estimated tax under this section for that tax plus the surcharge imposed under s. 77.93 before reduction for amounts paid as estimated tax under this section for that surcharge.

71.09(2) (2) Who shall pay. Every individual, estate and trust deriving income subject to taxation under this chapter, other than wages as defined in s. 71.63 (6) upon which taxes are withheld by the individual's employer under subch. X, shall pay estimated income tax, the surcharge under s. 77.93 and alternative minimum tax. This section does not apply to any person on active duty with the U.S. armed forces while stationed outside the continental United States. This section does not apply to any taxable year ending before the date 2 years after the date of a decedent's death with respect to the estate of such decedent or any trust all of which is treated under subpart E of part I of subchapter J of chapter 1 of the internal revenue code as owned by the decedent and to which the residue of the decedent's estate will pass under his or her will. This section does not apply to any trust that is subject to tax under this chapter on unrelated business taxable income as defined under section 512 of the internal revenue code. Those trusts are subject to estimated tax payments under s. 71.29.

71.09(3) (3) Farmers or fishers. Payments of estimated income tax required by sub. (2) from farmers or fishers may be made at any time on or before the 15th day of the first month of the succeeding taxable year.

71.09(4) (4) Farmers or fishers exception. Except as provided in sub. (1) (am), if on or before the first day of the 3rd month of the succeeding taxable year a farmer or a fisher files a return for the taxable year, for which estimated taxes were required on or before the 15th day of the first month of the succeeding taxable year under sub. (3), and pays in full the amount computed on the return as payable, then that payment satisfies any required estimated tax installments.

71.09(5) (5) Amount. The amount of the estimated income tax shall be the total estimated tax, including surtaxes, if any, reduced by the amount, if any, the individual, estate or trust determines will be withheld from wages pursuant to subch. X.

71.09(7) (7) Refund carry-forward. If the taxpayer claims a refund on any tax return and, concurrent with or subsequent to the filing of the return upon which such refund is claimed, is required to pay an estimated tax, and at the time of paying that tax the refund has not been paid, he or she may deduct the amount of such refund from the first installment of estimated taxes, and any excess from the succeeding installments. If a refund is paid after the due date of the last installment, its receipt shall be reflected on the income tax return covering the year. If the refund is disallowed in whole or in part after the due date of the last installment, that disallowance must be reflected on the income tax return covering the year.

71.09(8) (8) Prepayments. Any installment of the estimated tax under this section may be paid prior to the date prescribed for its payment.

71.09(9) (9) Short year. Application of this section to taxable years of less than 12 full months shall be made pursuant to rules of the department.

71.09(10) (10) Overpayment. When the amount of an installment payment of estimated tax exceeds the amount determined to be the correct amount of such installment payment, the overpayment shall be credited against the unpaid installment, if any.

71.09(11) (11) Exceptions to interest. No interest is required under s. 71.84 (1) if any of the following conditions apply:

71.09(11)(d) (d) The secretary of revenue determines that the taxpayer retired during the taxable year or during the preceding taxable year after having attained age 62 or becoming disabled except that this paragraph does not apply upon a showing by the department under s. 73.16 (4).

71.09(11)(e) (e) For taxable years beginning after December 31, 2008, the taxpayer qualifies for a federal extension of time to file under 26 USC 7508A due to a presidentially declared disaster or terroristic or military action.

71.09(11)(f) (f) The taxpayer has underpaid the taxpayer's estimated taxes due to the change in brackets under s. 71.06 (1p) (e) and (2) (g) 5. and (h) 5. This paragraph applies only in the first taxable year to which these bracket changes apply.