(b) (1) Except as otherwise provided, the domestic partner or former domestic partner of a taxpayer shall be treated as the spouse or former spouse of that taxpayer for purposes of applying provisions of this part, Part 10.2 (commencing with Section 18401), Part 10.7 (commencing with Section 21001), and Part 11 (commencing with Section 23001), and for purposes of applying provisions of the Internal Revenue Code that are applicable for purposes of this part, Part 10.2, Part 10.7, or Part 11.

(2) A domestic partner shall not be treated as the spouse of a taxpayer as required by paragraph (1) in the following circumstances:

(A) Where the treatment would result in the classification of a business entity for purposes of this part, Part 10.2, or Part 11 that would be different than the classification of that business entity for federal income tax purposes.

(B) Where the treatment required by paragraph (1) would result in disqualification for federal income tax purposes of a plan that otherwise qualifies under Section 401(a) of the Internal Revenue Code.

(C) Where the treatment would result in a tax-favored account that would not be qualified as a tax-favored account for federal income tax purposes. For purposes of this subparagraph, “tax-favored account” means an individual account, plan, or arrangement that is exempt from income tax under Chapter 1 of the Internal Revenue Code, including an individual retirement account, as described in Section 408 of the Internal Revenue Code, an Archer MSA, as described in Section 220 of the Internal Revenue Code, a qualified tuition program, as described in Section 529 of the Internal Revenue Code, and a Coverdell education savings account, as described in Section 530 of the Internal Revenue Code.

(3) The amendments made by the act adding this subdivision shall be operative for each taxable year beginning on or after January 1, 2007.