Partners or limited liability company members.

In determining Wisconsin adjusted gross income or Wisconsin taxable income of a partner or member, any applicable modification described in this section which relates to an item of partnership or limited liability company income, gain, loss or deduction shall be made in accordance with the partner’s or member’s distributive share, for federal income tax purposes, of the item to which the modification relates. Where a partner’s or member’s distributive share of any such item is not required to be taken into account separately for federal income tax purposes or the modification relates to no ascertainable item of the partnership or limited liability company income of the current year, each partner’s or member’s share of such modification shall be proportional to his or her distributive share for federal income tax purposes of partnership or company taxable income or loss generally.