Entities filing a partnership return. Except as described in paragraph (c) of this section, an entity that files a partnership return for any taxable year is subject to the provisions of subchapter C of chapter 63 of the Internal Revenue Code (subchapter C of chapter 63) with respect to such taxable year even if it is determined that the entity filing the partnership return was not a partnership for such taxable year. Accordingly, any partnership-related item (as defined in § 301.6241-1(a)(6)(ii)) and any person holding an interest in the entity, either directly or indirectly, at any time during that taxable year are subject to the provisions of subchapter C of chapter 63 for such taxable year.

Partnership return filed but no entity found to exist. Paragraph (a) of this section also applies where a partnership return is filed for a taxable year, but the IRS determines that no entity existed at all for such taxable year. For purposes of applying paragraph (a) of this section, the partnership return is treated as if it were filed by an entity.

Exceptions. Paragraph (a) of this section does not apply to—

Any taxable year for which an election under section 6221(b) is in effect, treating the return as if it were filed by a partnership for the taxable year to which the election relates; and

Any taxable year for which a valid section 761(a) election is made (regarding election out of subchapter K of chapter 1 of the Internal Revenue Code for certain unincorporated organizations).

Applicability date—(1) In general. Except as provided in paragraph (d)(2) of this section, this section applies to partnership taxable years beginning after December 31, 2017, and ending after August 12, 2018.

Election under § 301.9100-22 in effect. This section applies to any partnership taxable year beginning after November 2, 2015, and before January 1, 2018, for which a valid election under § 301.9100-22 is in effect.