(A) or (B) with respect to the taxpayer has the right to make any decision with respect to the investment of any amount in such account, or (G) files a consolidated return (within the meaning of section 1501) with the taxpayer for any taxable year which includes a portion of such period. (2) Determination of marital status (A) In general Except as provided in subparagraph (B), marital status shall be determined under section 7703. (B) Special rule for married individuals filing separately and living apart A husband and wife who— (i) file separate returns for any taxable year, and (ii) live apart at all times during such taxable year, shall not be treated as married individuals. (g) Regulations The Secretary shall prescribe such regulations or other guidance as may be appropriate to carry out this section, including regulations or guidance which require in appropriate cases a taxpayer to bifurcate derivatives described in subsection (d)(4) for purposes of applying this part or which may be necessary to prevent the avoidance of the purposes of subsection (f) (including treating persons as related parties if such persons are formed or availed of to avoid the purposes of such subsection). 493. Derivative defined (a) In general For purposes of this part, except as otherwise provided in this section, the term derivative means any contract (including any option, forward contract, futures contract, short position, swap, or similar contract) the value of which, or any payment or other transfer with respect to which, is (directly or indirectly) determined by reference to one or more of the following: (1) Any share of stock in a corporation. (2) Any partnership or beneficial ownership interest in a partnership or trust. (3) Any evidence of indebtedness. (4) Except as provided in subsection (b)(1), any real property. (5) Any commodity which is actively traded (within the meaning of section 1092(c)(4)). (6) Any currency. (7) Any rate, price, amount, index, formula, or algorithm. (8) Any other item as the Secretary may