majority interest taxable year
(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.
26 USC § 706(b)(4)
None identified, default scope is assumed to be the parent (part I) of this section.