((a)) ** Year in which partnership income is includible** In computing the taxable income of a partner for a taxable year, the inclusions required by section 702 and section 707(c) with respect to a partnership shall be based on the income, gain, loss, deduction, or credit of the partnership for any taxable year of the partnership ending within or with the taxable year of the partner.

((b)) ** Taxable year**

((1)) ** Partnership’s taxable year**

((A)) ** Partnership treated as taxpayer** The taxable year of a partnership shall be determined as though the partnership were a taxpayer.

((B)) ** Taxable year determined by reference to partners** Except as provided in subparagraph (C), a partnership shall not have a taxable year other than—

((i)) the majority interest taxable year (as defined in paragraph (4)),

((ii)) if there is no taxable year described in clause (i), the taxable year of all the principal partners of the partnership, or

((iii)) if there is no taxable year described in clause (i) or (ii), the calendar year unless the Secretary by regulations prescribes another period.

((C)) ** Business purpose** A partnership may have a taxable year not described in subparagraph (B) if it establishes, to the satisfaction of the Secretary, a business purpose therefor. For purposes of this subparagraph, any deferral of income to partners shall not be treated as a business purpose.

((2)) ** Partner’s taxable year** A partner may not change to a taxable year other than that of a partnership in which he is a principal partner unless he establishes, to the satisfaction of the Secretary, a business purpose therefor.

((3)) ** Principal partner** For the purpose of this subsection, a principal partner is a partner having an interest of 5 percent or more in partnership profits or capital.

((4)) ** Majority interest taxable year; limitation on required changes**

((A)) ** Majority interest taxable year defined** For purposes of paragraph (1)(B)(i)—

((i)) ** In general** The term “majority interest taxable year” means the taxable year (if any) which, on each testing day, constituted the taxable year of 1 or more partners having (on such day) an aggregate interest in partnership profits and capital of more than 50 percent.

((ii)) ** Testing days** The testing days shall be—

((I)) the 1st day of the partnership taxable year (determined without regard to clause (i)), or

((II)) the days during such representative period as the Secretary may prescribe.

((B)) ** Further change not required for 3 years** Except as provided in regulations necessary to prevent the avoidance of this section, if, by reason of paragraph (1)(B)(i), the taxable year of a partnership is changed, such partnership shall not be required to change to another taxable year for either of the 2 taxable years following the year of change.

((5)) ** Application with other sections** Except as provided in regulations, for purposes of determining the taxable year to which a partnership is required to change by reason of this subsection, changes in taxable years of other persons required by this subsection, section 441(i), section 584(i), section 644, or section 1378(a) shall be taken into account.

((c)) ** Closing of partnership year**

((1)) ** General rule** Except in the case of a termination of a partnership and except as provided in paragraph (2) of this subsection, the taxable year of a partnership shall not close as the result of the death of a partner, the entry of a new partner, the liquidation of a partner’s interest in the partnership, or the sale or exchange of a partner’s interest in the partnership.

((2)) ** Treatment of dispositions**

((A)) ** Disposition of entire interest** The taxable year of a partnership shall close with respect to a partner whose entire interest in the partnership terminates (whether by reason of death, liquidation, or otherwise).

((B)) ** Disposition of less than entire interest** The taxable year of a partnership shall not close (other than at the end of a partnership’s taxable year as determined under subsection (b)(1)) with respect to a partner who sells or exchanges less than his entire interest in the partnership or with respect to a partner whose interest is reduced (whether by entry of a new partner, partial liquidation of a partner’s interest, gift, or otherwise).

((d)) ** Determination of distributive share when partner’s interest changes**

((1)) ** In general** Except as provided in paragraphs (2) and (3), if during any taxable year of the partnership there is a change in any partner’s interest in the partnership, each partner’s distributive share of any item of income, gain, loss, deduction, or credit of the partnership for such taxable year shall be determined by the use of any method prescribed by the Secretary by regulations which takes into account the varying interests of the partners in the partnership during such taxable year.

((2)) ** Certain cash basis items prorated over period to which attributable**

((A)) ** In general** If during any taxable year of the partnership there is a change in any partner’s interest in the partnership, then (except to the extent provided in regulations) each partner’s distributive share of any allocable cash basis item shall be determined—

((i)) by assigning the appropriate portion of such item to each day in the period to which it is attributable, and

((ii)) by allocating the portion assigned to any such day among the partners in proportion to their interests in the partnership at the close of such day.

((B)) ** Allocable cash basis item** For purposes of this paragraph, the term “allocable cash basis item” means any of the following items with respect to which the partnership uses the cash receipts and disbursements method of accounting:

((i)) Interest.

((ii)) Taxes.

((iii)) Payments for services or for the use of property.

((iv)) Any other item of a kind specified in regulations prescribed by the Secretary as being an item with respect to which the application of this paragraph is appropriate to avoid significant misstatements of the income of the partners.

((C)) ** Items attributable to periods not within taxable year** If any portion of any allocable cash basis item is attributable to—

((i)) any period before the beginning of the taxable year, such portion shall be assigned under subparagraph (A)(i) to the first day of the taxable year, or

((ii)) any period after the close of the taxable year, such portion shall be assigned under subparagraph (A)(i) to the last day of the taxable year.

((D)) ** Treatment of deductible items attributable to prior periods** If any portion of a deductible cash basis item is assigned under subparagraph (C)(i) to the first day of any taxable year—

((i)) such portion shall be allocated among persons who are partners in the partnership during the period to which such portion is attributable in accordance with their varying interests in the partnership during such period, and

((ii)) any amount allocated under clause (i) to a person who is not a partner in the partnership on such first day shall be capitalized by the partnership and treated in the manner provided for in section 755.

((3)) ** Items attributable to interest in lower tier partnership prorated over entire taxable year** If—

((A)) during any taxable year of the partnership there is a change in any partner’s interest in the partnership (hereinafter in this paragraph referred to as the “upper tier partnership”), and

((B)) such partnership is a partner in another partnership (hereinafter in this paragraph referred to as the “lower tier partnership”),

((4)) ** Taxable year determined without regard to subsection (c)(2)(A)** For purposes of this subsection, the taxable year of a partnership shall be determined without regard to subsection (c)(2)(A).