Amendment SA51-AB100

AB100-SA51,3,2 1. A parent corporation and any corporation or chain of corporations that are connected to the parent corporation by direct or indirect ownership by the parent corporation if the parent corporation owns stock representing more than 50 percent of the voting power of at least one of the connected corporations or if the parent corporation or any of the connected corporations own stock that cumulatively represents more than 50 percent of the voting power of each of the connected corporations.

AB100-SA51,3,5 2. Any 2 or more corporations if a common owner directly or indirectly owns stock representing more than 50 percent of the voting power of the corporations or the connected corporations.

AB100-SA51,3,9 3. A partnership or limited liability company if a parent corporation or any corporation connected to the parent corporation by common ownership directly or indirectly owns more than a 50 percent interest in the capital and profits of the partnership or limited liability company.

AB100-SA51,3,11 4. Any 2 or more corporations if stock representing more than 50 percent of the voting power in each corporation is interest that cannot be separately transferred.

AB100-SA51,3,16 5. Any 2 or more corporations if stock representing more than 50 percent of the voting power in each corporation is directly owned by, or for the benefit of, family members. In this subdivision, "family member" means an individual related by blood, marriage, or adoption within the 2nd degree of kinship as computed under s. 852.03 (2), 1995 stats., or the spouse of such an individual.

AB100-SA51,3,21 6. A corporation, partnership, or limited liability company if a parent corporation or any corporation connected to the parent corporation by common ownership does not hold more than a 50 percent ownership interest in the corporation, partnership, or limited liability company but effectively controls the corporation, partnership, or limited liability company.

AB100-SA51,3,22 (e) "Corporation" has the meaning given in s. 71.22 (1) or 71.42 (1).

AB100-SA51,3,23 (f) "Department" means the department of revenue.

AB100-SA51,4,3 (g) "Designated agent" means the taxpayer member of a commonly controlled group that files a group return on behalf of the taxpayer members of a combined reporting group.

AB100-SA51,4,5 (h) "Group return" means a tax return filed on behalf of the taxpayer members of a combined reporting group.

AB100-SA51,4,8 (i) "Intercompany transaction" means a transaction between corporations, partnerships, or limited liability companies that become members of the same combined reporting group immediately after the transaction.

AB100-SA51,4,10 (im) "Partnership" means any entity considered a partnership under section 7701 of the Internal Revenue Code.

AB100-SA51,4,13 (j) "Separate return" means a return filed by a corporation, regardless of whether the corporation is a member of a combined reporting group or is required to file a tax return under s. 71.24 or 71.44.

AB100-SA51,4,16 (k) "Taxpayer member" means a corporation that is subject to tax under s. 71.23 (1) or (2) or 71.43, that is a member of a combined reporting group, and that files a combined report under this section.

AB100-SA51,4,22 (L) "Top-tier corporation" means a member of a commonly controlled group that is not connected with a parent corporation by stock ownership or interest ownership as described in par. (d), is a parent corporation, or is a brother-sister parent corporation, regardless of whether it is doing business in this state or deriving income from sources in this state, and regardless of whether its income and apportionment factors are excluded from a combined report filed under this section.

AB100-SA51,5,6 (m) "Unitary business" includes the business activities or operations of an entity that are of mutual benefit to, integrated with, or dependent upon or that contribute to activities of at least one other entity, including transactions that serve an operational function, as determined by the department. Two or more businesses are presumed to be a unitary business if the businesses have unity of ownership, operation, and use as indicated by centralized management or a centralized executive force; centralized purchasing, advertising, or accounting; intercorporate sales or leases; intercorporate services; intercorporate debts; intercorporate use of proprietary materials; interlocking directorates; or interlocking corporate officers.

AB100-SA51,5,15 (2) Corporations required to use combined reporting. (a) Except as provided in par. (b), and subject to sub. (6), a corporation that is subject to the tax imposed under s. 71.23 (1) or (2) or 71.43, that is a member of a commonly controlled group, and that is engaged, in whole or in part, in a unitary business with one or more members of the commonly controlled group shall compute the corporation's income attributable to this state by using the income computation under s. 71.26 or 71.45, the apportionment formula under s. 71.25 (6) or 71.45, and the tax credits under s. 71.28 or 71.47 of all of the following that are members of the commonly controlled group:

AB100-SA51,5,20 1. Any corporation organized or incorporated under the laws of the United States, any state of the United States, the District of Columbia, the Commonwealth of Puerto Rico, any possession of the United States, or any political subdivision of the United States, including corporations under sections 931 to 936 of the Internal Revenue Code.

AB100-SA51,5,22 2. Any domestic international sales corporation under sections 991 to 994 of the Internal Revenue Code.

AB100-SA51,5,24 3. Any foreign sales corporation under sections 921 to 927 of the Internal Revenue Code.

AB100-SA51,6,2 4. Any export trade corporation under sections 970 and 971 of the Internal Revenue Code.

AB100-SA51,6,7 5. Any corporation, regardless of its place of incorporation if the average of its property factor under s. 71.25 (7) and its payroll factor under s. 71.25 (8), for property and payroll within the United States and computed on an annual basis, is at least 20 percent during any part of the taxable year that a corporation is a member of the commonly controlled group.

AB100-SA51,6,11 6. Any corporation not described in subds. 1. to 5. to the extent of the corporation's income within the United States and the corporation's property factor under s. 71.25 (7) and payroll factor under s. 71.25 (8) assignable to a location within the United States.

AB100-SA51,6,22 (b) A corporation that is subject to the tax imposed under s. 71.23 (1) or (2) or 71.43, that is a member of a commonly controlled group, and that is engaged, in whole or in part, in a unitary business with one or more members of the commonly controlled group may, subject to sub. (6), compute the corporation's income attributable to this state by using the income computation under s. 71.26 or 71.45, the apportionment formula under s. 71.25 (6) or 71.45, and the tax credits under s. 71.28 or 71.47 of all the members of the commonly controlled group, regardless of the country in which any member of the commonly controlled group is organized or incorporated or conducts business, if all top-tier corporations that are members of the commonly controlled group elect under sub. (3) to compute the corporation's income as provided under this paragraph.

AB100-SA51,7,5 (3) Computation election. (a) A top-tier corporation that is a member of a commonly controlled group may elect on the commonly controlled group's behalf, and in the manner prescribed by the department, to compute the income of each corporation that is a member of the commonly controlled group under sub. (2) (b). If more than one member of the commonly controlled group is a top-tier corporation, an election under this subsection is not effective unless all top-tier corporations elect on the commonly controlled group's behalf, and in the manner prescribed by the department, to compute income under sub. (2) (b).

AB100-SA51,7,13 (b) A top-tier corporation shall file an election made under par. (a) with the department before the last day of the taxable year. The top-tier corporation shall designate a taxable year that corresponds with the taxable year of any taxpayer member that is subject to the tax imposed under s. 71.23 (1) or (2) or 71.43. If the top-tier corporation fails to file the election before the last day of the taxable year designated under this paragraph, all members of the commonly controlled group to which the top-tier corporation belongs, including the top-tier corporation, shall compute income under sub. (2) (a).

AB100-SA51,7,24 (c) Except as provided under par. (d), the members of the commonly controlled group subject to an election under this subsection shall compute their income under sub. (2) (b) for 7 taxable years, beginning with the taxable year designated under par. (b). Thereafter, the members of the commonly controlled group shall compute their income under sub. (2) (b) for periods of 7 taxable years and until any top-tier corporation that is a member of the commonly controlled group notifies the department, in a manner prescribed by the department, before the last day of the last taxable year in any period of 7 taxable years that the top-tier corporation is terminating the election under this subsection. A termination under this paragraph takes effect on the first day of the first taxable year beginning after the top-tier corporation notifies the department under this paragraph.

AB100-SA51,8,5 (d) The department may grant a request by a top-tier corporation to terminate an election under this subsection before the first period of 7 taxable years under par. (c) expires, if the top-tier corporation shows good cause for granting the request, as determined by the department and consistent with section 1502 of the Internal Revenue Code.

AB100-SA51,8,10 (e) Except as provided in par. (f), if an election by a top-tier corporation on behalf of the members of a commonly controlled group under this subsection is terminated, no top-tier corporation may make an election on behalf of the members of the same commonly controlled group until 7 taxable years have elapsed from the day that the termination of the original election took effect.

AB100-SA51,8,15 (f) The department may grant a request by a top-tier corporation to make an election under this subsection before the period of 7 taxable years under par. (e) have elapsed, if the top-tier corporation shows good cause for granting the request, as determined by the department and consistent with section 1502 of the Internal Revenue Code.

AB100-SA51,9,2 (4) Accounting period. For purposes of this section, the income under ss. 71.26 and 71.45, the apportionment factors under ss. 71.25 and 71.45, and the tax credits under ss. 71.28 and 71.47 of all corporations that are members of a combined reporting group shall be determined by using the same accounting period. If the combined reporting group has a common parent corporation, the accounting period of the common parent corporation shall be used to determine the income, the apportionment factors, and the tax credits of all the corporations that are members of the combined reporting group. If the combined reporting group has no common parent corporation, the income, the apportionment factors, and the tax credits of the combined reporting group shall be determined using the accounting period of the member of the combined reporting group that has the most significant operations on a recurring basis in this state, as determined by the department.

AB100-SA51,9,11 (5) Filing returns. (a) Corporations with the same accounting period. Corporations that must file a combined report under this section and that have the same accounting period may file a group return, as prescribed by the department, that reports the aggregate state franchise or state income tax liability of all of the members of the combined reporting group. Corporations that are required to file a combined report under this section may file separate returns reporting the respective apportionment of the corporation's state franchise or state income tax liability as determined under sub. (2), if each corporation filing a separate return pays its own apportionment of its state franchise or state income tax liability.

AB100-SA51,9,25 (b) Corporations with different accounting periods. Corporations that are required to file a combined report and that have different accounting periods shall file separate returns and shall use the actual figures from the corporations' financial records to determine the proper income and income-related computations to convert to a common accounting period. Corporations that are required to file a combined report may use a proportional method to convert income to a common accounting period if the results of the proportional method do not materially misrepresent the income apportioned to this state. The apportionment factors under ss. 71.25 and 71.45 and the tax credits under ss. 71.28 and 71.47 shall be computed according to the same method used to determine the income under ss. 71.26 and 71.45 for the common accounting period. If a corporation performs an interim closing of its financial records to determine the income attributable to the common accounting period, the actual figures from the interim closing shall be used to convert the apportionment factors and tax credits to the common accounting period.

AB100-SA51,10,17 (c) Designated agent. 1. For corporations that are subject to this section and that file a group return under par. (a), the parent corporation of the combined reporting group is the sole designated agent for each member of the combined reporting group including the parent corporation, if the parent corporation is a taxpayer member of the combined reporting group and income of the parent corporation is included on the group return. If the parent corporation is not a taxpayer member or if the parent corporation's income is not included on the group return, the taxpayer members may appoint a taxpayer member to be the designated agent. If the parent corporation of the combined reporting group is not eligible to be the designated agent and no taxpayer member is appointed to be the designated agent, the designated agent is the taxpayer member that has the most significant operations in this state on a recurring basis, as determined by the department. The designated agent, as determined under this subdivision, remains the designated agent until the designated agent is no longer a taxpayer member or until the taxpayer members appoint a different designated agent. If the designated agent changes, the combined reporting group shall notify the department of such a change, in a manner prescribed by the department.

AB100-SA51,11,15 2. The designated agent shall file the group return under par. (a), shall file for any extensions under s. 71.24 (7) or 71.44 (3), shall file amended reports and claims for refund or credit, and shall send and receive all correspondence with the department regarding a group return. Any notice the department sends to the designated agent is considered a notice sent to all members of the combined reporting group. Any refund with respect to a group return shall be paid to and in the name of the designated agent and shall discharge any liability of the state to any member of a combined reporting group regarding the refund. The combined reporting group filing a group return under par. (a) shall pay all taxes, including estimated taxes, in the designated agent's name. The designated agent shall participate on behalf of the members of the combined reporting group in any investigation or hearing requested by the department regarding a group return and shall produce all information requested by the department regarding a group return. The designated agent may execute a power of attorney on behalf of the members of the combined reporting group. The designated agent shall execute waivers, closing agreements, and other documents regarding a group return filed under par. (a) and any waiver, agreement, or document executed by the designated agent shall be considered as executed by all members of the combined reporting group. If the department acts in good faith with a combined reporting group member that represents itself as the designated agent for the combined reporting group but that combined reporting group member is not the designated agent, any action taken by the department with that combined reporting group member has the same effect as if that combined reporting group member were the actual designated agent for the combined reporting group.

AB100-SA51,11,19 (d) Part-year members. If a corporation becomes a member of a combined reporting group or ceases to be a member of a combined reporting group after the beginning of a common accounting period, the corporation's income shall be apportioned to this state as follows:

AB100-SA51,12,3 1. If the corporation is required to file 2 or more short-period federal returns for the common accounting period, the income for the short period in which the corporation was a member of a combined reporting group shall be determined as provided under sub. (2), the corporation shall join in filing a combined report for that short period, and the corporation may join in filing a group return for that short period. The income for the remaining short period shall be reported on a separate return under s. 71.26 or 71.45. If the corporation becomes a member of another combined reporting group in the remaining short period, the corporation's income shall be determined for the remaining short period as provided under sub. (2).

AB100-SA51,12,5 2. If the corporation is not required to file federal short-period returns, the corporation shall file a separate return. Income shall be determined as follows:

AB100-SA51,12,7 a. As provided under sub. (2) for any period that the corporation was a member of a combined reporting group.

AB100-SA51,12,9 b. As a separate entity under s. 71.26 or 71.45 for any period that the corporation was not a member of a combined reporting group.

AB100-SA51,12,13 (e) Amended group return. The election to file a group return under this section applies to an amended group return that includes the same corporations that joined in the filing of the original group return. Under this section, an amended group return shall be filed as follows:

AB100-SA51,12,22 1. If an election to file a group return that is in effect for a taxable year is revoked for the taxable year because the combined reporting group that filed the group return is not subject to sub. (2), as determined by the department, the designated agent for the combined reporting group may not file an amended group return. The designated agent and each corporation that joined in filing the group return shall file a separate amended return. To compute the tax due on a separate amended return, a corporation that files a separate amended return shall consider all of the payments, credits, or other amounts, including refunds, that the designated agent allocated to the corporation.

AB100-SA51,13,2 2. If a change in tax liability under this section is the result of the removal of a corporation from a combined reporting group because the corporation was not eligible to be a member of the combined reporting group for the taxable year, as determined by the department, the designated agent shall file an amended group return and the ineligible corporation shall file a separate amended return.

AB100-SA51,13,8 3. If a corporation erroneously fails to join in the filing of a group return, the designated agent shall file an amended group return that includes the corporation. If a corporation that erroneously fails to join in the filing of a group return has filed a separate return, the corporation shall file an amended separate return that shows no net income, overpayment, or underpayment, and shows that the corporation has joined in the filing of a group return.

AB100-SA51,13,10 (6) Income computation under combined reporting. For the purposes of sub. (2), income attributable to this state shall be determined as follows:

AB100-SA51,13,25 (a) Determine the net income of each member of a combined reporting group under s. 71.26 or 71.45, as appropriate, before deducting net business losses. A member of a combined reporting group may determine its net loss or net income under a method of accounting or an election authorized under s. 71.26 (3) (y), 71.30 (1), 71.45 (2) (a) 13., or 71.49 (2), as appropriate, regardless of the accounting method used to determine the net loss or net income of other members of the combined reporting group. After a member establishes an accounting method, or makes any election under this section, the member's net loss or net income shall be consistently determined in the combined report of all members of the combined reporting group and in the group return filed by the taxpayer members or in the separate return filed by the members. If a corporation is engaged in 2 or more trades or businesses that are required to use different apportionment formulas under s. 71.25 or 71.45, the net income for each trade or business shall be computed separately. A unitary business with operations in a foreign country shall compute its net loss or net income as provided by rule by the department.

AB100-SA51,14,2 (b) Adjust each member's income, as determined under par. (a), as provided under s. 71.30.

AB100-SA51,14,8 (c) From the amount determined under par. (b), subtract intercompany transactions, as provided by rule by the department, such that intercompany accounts of assets, liabilities, equities, income, costs, or expenses are excluded from the income determination to accurately reflect the income, the apportionment factors, and the tax credits in a combined report that is filed under this section. An intercompany transaction includes the following:

AB100-SA51,14,11 1. Income or gain from sales, exchanges, contributions, or other transfers of tangible or intangible property from a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,14,13 2. Annual rent paid by a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,14,15 3. Annual license fees or royalties paid by a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,14,18 4. Loans, advances, receivables, and similar items that one member of the combined reporting group owes to another member of the combined reporting group, including interest income and interest expense related to these items.

AB100-SA51,14,20 5. Stock or other equity of a member of the combined reporting group that is owned or controlled by another member of the combined reporting group.

AB100-SA51,14,23 6. Except as provided by rule by the department, dividends paid out of earnings or profits and paid by a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,14,25 7. Management or service fees paid by a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,15,2 8. Income or expenses allocated or charged by a member of the combined reporting group to another member of the combined reporting group.

AB100-SA51,15,6 (d) From the amount determined under par. (c) for each member of a combined reporting group, subtract nonapportionable income, net of related expenses, and add nonapportionable losses, net of related expenses, to determine each member's apportionable net income or apportionable net loss.

AB100-SA51,15,9 (e) Calculate the apportionment factors under sub. (7) and multiply each member's apportionable net income or apportionable net loss, as determined under par. (d), by the member's apportionment factor as determined under sub. (7).

AB100-SA51,15,11 (f) For each corporation, combine the amounts determined under par. (e) for each trade or business.

AB100-SA51,15,14 (g) To the amounts determined under par. (f), add each member's nonapportionable income attributable to this state and subtract each member's nonapportionable losses attributable to this state.

AB100-SA51,15,16 (h) If the combined reporting group is not filing a group return, combine the amounts determined under par. (g) for all members of the combined reporting group.

AB100-SA51,15,19 (i) If the combined reporting group is filing a group return, combine the amounts determined under par. (g) for all members of the combined reporting group that join in filing the group return.

AB100-SA51,15,21 (j) From the amount determined under par. (h) or (i), as appropriate, subtract the combined reporting group's net operating loss as determined under sub. (8).

AB100-SA51,15,23 (7) Apportionment factor computation under combined reporting. For the purposes of sub. (2), this state's apportionment factors are determined as follows:

AB100-SA51,16,3 (a) 1. Determine the numerator and the denominator of the apportionment factors as determined under s. 71.25 or 71.45, as appropriate, for each member of the combined reporting group, except as provided in subd. 2.

AB100-SA51,16,13 2. If a member of a combined reporting group is not subject to the tax imposed under s. 71.23 or 71.43 because it does not have sufficient connection to this state as a separate entity for income or franchise tax purposes, as determined by the department, the numerator of the member's sales factor under s. 71.25 (9) or apportionment factor under s. 71.45 (3) is zero. If a member of a combined reporting group is a corporation engaged in business wholly within this state, as provided under s. 71.25 (4), the numerator and denominator of the member's apportionment factors are the same. If a member of a combined reporting group is not subject to an income or franchise tax as a separate entity in the state to which a sale is attributed, the sale is attributed to this state.

AB100-SA51,16,15 (b) Subtract intercompany transactions under sub. (6) (c) from both the numerators and the denominators as determined under par. (a).

AB100-SA51,16,18 (c) Add the denominators of the apportionment factors for each member of the combined reporting group, as determined under par. (b), to arrive at the combined denominator.

AB100-SA51,16,21 (d) Compute each corporation's apportionment factors by dividing the corporation's numerator as determined under par. (b) by the combined denominator as determined under par. (c).

AB100-SA51,17,5 (8) Net business loss carry-over. (a) For taxable years beginning after December 31, 2005, any net business loss of a corporation that is a member of a combined reporting group as determined under sub. (6) for the taxable year that is not offset against the net income of the other members of the combined reporting group in the same taxable year may be carried forward as provided under s. 71.26 (4), except that any net business loss carried forward to a subsequent taxable year may be offset against either the net income of the corporation that incurred the net business loss or the net income of the combined reporting group of which the corporation is a member, in the manner prescribed by rule by the department.

AB100-SA51,17,9 (b) A corporation that is a member of a combined reporting group may not carry forward a net business loss from a taxable year beginning before January 1, 2006, if the corporation was not subject to the tax imposed under s. 71.23 or 71.43 for the same taxable year.

AB100-SA51,17,20 (c) A corporation that is a member of a combined reporting group and that incurred a Wisconsin net business loss in a taxable year beginning before January 1, 2006, that has not been offset against the corporation's net income in subsequent taxable years may offset the remaining net business loss against the corporation's net income as determined under sub. (6). If the corporation joins in filing a group return under sub. (5) and the corporation's remaining net business loss exceeds the corporation's net income as determined under sub. (6) for the first taxable year beginning after December 31, 2005, that the corporation is subject to this section, the corporation may annually offset up to 20 percent of the remaining net business loss against the net income of the other members of the combined reporting group that join in filing a group return under sub. (5).

AB100-SA51,18,5 (9) Net income or loss for corporations with different accounting periods. If a taxpayer member has a different accounting period from the common accounting period of the combined reporting group, the combined reporting group shall assign the combined report income or loss for the combined reporting group, as determined under sub. (6), proportionally to the number of months in the taxpayer member's taxable year that are wholly or partly within the combined reporting group's common accounting period. The total amount of income or loss assigned to a taxpayer member under this subsection for the portions of the common accounting period that are included in the taxpayer member's taxable period shall be aggregated or netted to determine the taxpayer member's apportionable income.

AB100-SA51,18,7 (10) Net tax liability. (a) A corporation that files a separate return under this section shall determine its net tax liability as follows:

AB100-SA51,18,9 1. Multiply the amount determined under sub. (6) (i) for the corporation by the tax rate under s. 71.27 or 71.46, as appropriate.

AB100-SA51,18,14 2. From the amount determined under subd. 1., subtract the corporation's tax credits under s. 71.28 or 71.47 based on the corporation's expenses. The corporation may not offset any of its tax credits, or tax credit carry-forwards, against the tax liability of any other member of the combined reporting group to which the corporation belongs.

AB100-SA51,18,16 (b) A combined reporting group that files a group return under this section shall determine its net tax liability as follows:

AB100-SA51,18,18 1. Multiply the amount determined under sub. (6) (i) for the combined reporting group by the tax rate under s. 71.27 or 71.46, as appropriate.

AB100-SA51,18,20 2. From the amount determined under subd. 1., subtract the tax credits under ss. 71.28 and 71.47 for all taxpayer members of the combined reporting group.

AB100-SA51,19,2 (11) Estimated tax payments. (a) For the first 2 taxable years that a group return is filed under this section, estimated taxes under ss. 71.29 and 71.48 may be paid on a group basis or on a separate basis. The amount of any separate estimated taxes paid in the first 2 taxable years that a group return is filed shall be credited against the group's tax liability. The designated agent shall notify the department of any estimated taxes paid on a separate basis in the first 2 taxable years that a group return is filed.

AB100-SA51,19,15 (b) If a group return is filed for 2 consecutive taxable years, estimated taxes under ss. 71.29 and 71.48 shall be paid on a group basis for each subsequent taxable year until such time as separate returns are filed by the corporations that were members of a combined reporting group that filed group returns under this section. For each taxable year in which combined estimated taxes are paid under this subsection, the department shall consider the combined reporting group filing a group return to be one taxpayer for purposes of computing interest on the underpayment of estimated taxes. If a corporation subject to this section files a separate return in a taxable year following a year in which the corporation joined in filing a group return, the amount of any estimated tax payments made on a group basis for the previous year shall be credited against the tax liability of the corporation that files a separate return, as allocated by the designated agent with the department's approval.

AB100-SA51,19,20 (c) If a combined reporting group pays estimated taxes on a group basis for a taxable year or for any part of a taxable year, and the members of the combined reporting group file separate returns for the taxable year, the designated agent, with the department's approval, shall allocate the estimated tax payments among the members of the combined reporting group.

AB100-SA51,19,25 (d) If estimated taxes are paid on a group basis for a taxable year but the group does not file a group return for the taxable year and did not file a group return for the previous taxable year, the estimated tax shall be credited to the member of the combined reporting group that made the estimated tax payment on the group's behalf.

AB100-SA51,20,3 (e) If a combined reporting group that will file a group return applies for a refund of estimated taxes under s. 71.29 (3m), the department shall determine the combined reporting group's eligibility for a refund on a group basis.

AB100-SA51,20,6 (12) Interest for underpayment of estimated tax. (a) General. The amount of interest that is due for an underpayment of estimated taxes under sub. (11) shall be computed as follows:

AB100-SA51,20,10 1. For the first year in which a combined reporting group files a group return, the amount of interest that is due for an underpayment of estimated taxes shall be determined by using the aggregate of the tax and income shown on the returns filed by the members of the combined reporting group for the previous year.

AB100-SA51,20,15 2. For any year in which a combined reporting group files a group return, the department shall determine if the combined reporting group qualifies for the exception to interest under s. 71.29 (7) (b) by using the aggregate of the amount of the tax liability and the amount of the net income of all members of the combined reporting group.

AB100-SA51,20,20 3. For any year in which a combined reporting group files a group return, the department shall determine if the installment provisions under s. 71.29 (9) or (10) apply to the combined reporting group by using the aggregate of the amount of the tax liability and the amount of the net income of all members of the combined reporting group.

AB100-SA51,21,2 4. For estimated taxes paid under sub. (11) (c), the amount of interest that is due from a member of a combined reporting group for an underpayment of estimated taxes paid by the member shall be determined by using the member's separate items from the group return filed for the previous year and the member's allocated share of the combined estimated tax payments for the current year. The designated agent shall report the member's allocated share of the combined estimated tax payments for the current year to the department, in the manner prescribed by the department.