(1g)    In this section:

      (a)    “Apportionment factor” has the meaning under s. 76.28 (1) (a).

      (b)    “Book cost of utility plant” has the meaning set forth in the uniform system of accounts prescribed by the U.S. rural electrification administration in bulletin 181-1, dated January 1, 1978.

      (c)    “Electric cooperative” means a cooperative association organized under ch. 185 that carries on the business of generating, transmitting or distributing electric energy to its members at wholesale or retail.

      (d)    “Gross revenues” means total operating revenues, except revenues for interdepartmental sales and for interdepartmental rents, less deductions from the sales and use tax under s. 77.61 (4) and, in respect to any electric cooperative that purchases more than 50 percent of the power it sells, less the actual cost of power purchased for resale by an electric cooperative, if the revenue from that purchased electric power is included in the seller’s gross revenues or if the electric cooperative purchased more than 50 percent of the power it sold in the year prior to January 1, 1988, from a seller located outside this state. For an electric cooperative, “gross revenues” does not include grants awarded to the electric cooperative under s. 16.958 (2) (b). For a retail electric cooperative, “gross revenues” does not include low-income assistance fees collected by the retail electric cooperative under s. 16.957 (5) (a), low-income assistance fees received by the retail electric cooperative from a retail electric cooperative or municipal utility under a joint program established under s. 16.957 (5) (f). For a wholesale supplier, as defined in s. 16.957 (1) (w), “gross revenues” does not include any low-income assistance fees that are received from a municipal utility, as defined in s. 16.957 (1) (q), or retail electric cooperative or under a joint program established under s. 16.957 (5) (f).

      (dm)    “Municipal utility” has the meaning given in s. 16.957 (1) (q).

      (e)    “Payroll factor” has the meaning under s. 76.28 (1) (f).

      (f)    “Property factor” has the meaning under s. 76.28 (1) (g).

      (fm)    “Retail electric cooperative” has the meaning given in s. 16.957 (1) (t).

      (g)    “Sales factor” means a fraction the numerator of which is the electric cooperative’s total sales of electricity in this state, not including sales to out-of-state purchasers that are delivered to transmission facilities in this state, for the tax period and the denominator of which is the electric cooperative’s total sales of electricity for the tax period.

      (h)    “Tax period” has the meaning under s. 76.28 (1) (i).

   (1r)   Except as provided in s. 76.29, every electric cooperative shall pay, in lieu of other general property and income or franchise taxes, an annual license fee equal to its apportionment factor multiplied by its gross revenues; excluding for the tax period, as defined in s. 76.29 (1) (f), gross revenues that are subject to the license fee under s. 76.29; multiplied by 3.19 percent. Real estate and personal property not used primarily for the purpose of generating, transmitting or distributing electric energy are subject to general property taxes. If a general structure is used in part to generate, transmit or distribute electric energy and in part for nonoperating purposes, the license fee imposed by this section is in place of the percentage of all other general property taxes that fairly measures and represents the extent of the use in generating, transmitting or distributing electric energy, and the balance is subject to local assessment and taxation, except that the entire general structure is subject to special assessments for local improvements.

   (2)   Every electric cooperative shall on or before March 15 in each year make and return to the department of revenue, in the form and upon the forms that the department prescribes, a true statement of the gross receipts from the operation of the cooperative’s business during the preceding calendar year together with such other information that the department requires to enforce this section. The statement shall be verified by the president and treasurer of the electric cooperative making the return. Upon written request, the department may grant an extension for filing the return, not to exceed 30 days. If any electric cooperative fails to file the return within the time prescribed by law, or as extended by the department, the department shall add to the taxes due from the electric cooperative $25, and the electric cooperative may not contest the imposition of that penalty in any action or proceeding.

   (3)   On or before May 1 in each year, the department of revenue shall compute and assess the license fees provided for in sub. (1r) and certify the amounts due the secretary of administration. The department shall notify each electric cooperative of the amount of the license fees so assessed. The fees shall become delinquent if not paid when due and when delinquent shall be subject to interest at the rate of 1.5 percent per month on the amount of license fee until paid. The interest shall be collected by the department and, upon collection, forwarded to the secretary of administration and retained by the state. The payment dates provided for in sub. (3a) shall apply.

   (3a)   License fees due under this section shall be paid to the department on an estimated basis. Payments of semiannual installments of the estimated tax liability for the subsequent year shall be due on or before May 10 and November 10 of the current year. With respect to the license fee assessment under sub. (3), each electric cooperative shall on each May 10 pay or be credited an amount which is equal to the difference between the May 1 assessment and the sum of the semiannual installment payments made in the preceding calendar year. The additional amount shall be added to the semiannual installment due on May 10. If there has been an overpayment the amount of the overpayment shall be credited to the semiannual installment due May 10. If any electric cooperative fails to make semiannual payments of at least 55 percent of the tax assessed for the current calendar year or 50 percent of the tax assessed for the subsequent calendar year, any amounts not paid when due shall become delinquent and shall be subject to interest under sub. (3). Associations with a liability under this section of less than $2,000 are not required to make semiannual payments but shall pay the full amount of license fees due on or before May 10 of the year of assessment.

   (4)   All license fees provided in sub. (1r) shall be deposited in the general fund for use of the state.

   (5)   Additional assessments may be made, if notice of such assessment is given, within 4 years of the date the annual return was filed, but if no return was filed, or if the return filed was incorrect and was filed with intent to defeat or evade the tax, an additional assessment may be made at any time upon the discovery of gross revenues by the department. Refunds may be made if a claim for the refund is filed in writing with the department within 4 years of the date the annual return was filed. Refunds shall bear interest at the rate of 3 percent per year and shall be certified by the department to the secretary of administration who shall audit the amounts of such overpayments and pay the amount audited. Additional assessments shall bear interest at the rate of 12 percent per year from the time they should have been paid to the date upon which they shall become delinquent if unpaid.

   (6)   All additional assessments and claims for refund shall be subject to the same procedure for review and final determination as is provided with respect to additional assessments and refunds of income or franchise taxes under chs. 71 and 73, except that appeals of denials of claims for refunds shall be made directly to the tax appeals commission and except as such procedure conflicts with this section.