underlying investment means, with respect to any derivative, any item— (i) which is described in any of the paragraphs (1) through (8) of section 493(a) (or any item substantially the same as any such item), and (ii) by reference to which the value of the derivative is determined either directly or indirectly. (B) Coordination with section 475 In the case of a dealer in securities to which section 475 applies (and a dealer in commodities with respect to which an election is in effect under section 475(e)), such term shall not include any item which, but for this subparagraph, would be treated as an underlying investment if such item is treated as a security under section 475 (including a commodity treated as a security under section 475(e)). (2) Establishment of investment hedging unit A taxpayer shall be treated as having established an investment hedging unit with respect to an underlying investment— (A) in the case of a taxpayer with an election in effect under subsection (b) with respect to the underlying investment, as of the date the election takes effect, and (B) in the case of any other taxpayer, as of the beginning of each applicable hedging period with respect to the underlying investment. (3) Related parties, etc For purposes of this section— (A) Attribution between related persons Any derivative or underlying investment held by a related party (within the meaning of subsection (f)) with respect to the taxpayer shall be treated as held by the taxpayer. (B) Certain flowthrough entities If part or all of the income, gain, loss, or expense with respect to a derivative or underlying investment held by a partnership, trust, or other entity would properly be taken into account for purposes of this chapter by the taxpayer, then, except to the extent otherwise provided in regulations, such derivative or investment shall be treated as held by the taxpayer. (f) Related party For purposes of this section— (1) In general A person is a related party to the taxpayer if, with respect to any period during which a