15-30-3312. Composite returns and tax. (1) A partnership or S. corporation may elect to file a composite return and pay a composite tax on behalf of participants. A participant is a partner, shareholder, member, or other owner who:

(a) is a nonresident individual, a foreign C. corporation, or a pass-through entity whose only Montana source income for the tax year is from the entity and other partnerships or S. corporations electing to file the composite return and pay the composite tax on behalf of that partner, shareholder, member, or other owner; and

(b) consents to be included in the filing.

(2) (a) Each participant's composite tax liability is the product obtained by:

(i) determining the tax that would be imposed, using the rates specified in 15-30-2103, on the sum obtained by subtracting the allowable standard deduction for a single individual and one exemption allowance from the participant's share of the entity's income from all sources as determined for federal income tax purposes; and

(ii) multiplying that amount by the ratio of the entity's Montana source income to the entity's income from all sources for federal income tax purposes.

(b) A participant's share of the entity's income is the aggregate of the participant's share of the entity's income, gain, loss, or deduction or item of income, gain, loss, or deduction.

(3) The composite tax is the sum of each participant's composite tax liability.

(4) The electing entity:

(a) shall remit the composite tax to the department;

(b) must be responsible for any assessments of additional tax, penalties, and interest, which additional assessments must be based on the total liability reflected in the composite return;

(c) shall represent the participants in any appeals, claims for refund, hearing, or court proceeding in any matters relating to the filing of the composite return;

(d) shall make quarterly estimated tax payments and be subject to the underpayment interest as prescribed by 15-30-2512(5)(a) computed on the composite tax liability included in the filing of a composite return; and

(e) shall retain powers of attorney executed by each participant included in the composite return, authorizing the entity to file the composite return and to act on behalf of each participant.

(5) The composite return must be made on forms the department prescribes and filed on or before the due date, including extensions, for filing the entity information return. The composite return is in lieu of an individual income tax return required under 15-30-2602 and 15-30-2604, a corporate income tax return required under 15-31-111, and an alternative corporate income tax return required under 15-31-403.

(6) The composite tax is in lieu of the taxes imposed under:

(a) 15-30-2103 and 15-30-2104;

(b) 15-31-101 and 15-31-121; and

(c) 15-31-403.

(7) The department may adopt rules that are necessary to implement and administer this section.