26 CFR §1.1502-30

1. (a)Scope. This section provides rules for determining the basis of the stock of an acquiring corporation as a result of a triangular reorganization. The definitions and nomenclature contained in § 1.358-6 apply to this section.
2. (b)General rules
   1. (1)Forward triangular merger, triangular C reorganization, or triangular B reorganization. P adjusts its basis in the stock of S as a result of a forward triangular merger, triangular C reorganization, or triangular B reorganization under § 1.358-6(c) and (d), except that § 1.358-6 (c)(1)(ii) and (d)(2) do not apply. Instead, P adjusts such basis by taking into account the full amount of—
      1. (i)T liabilities assumed by S or the amount of liabilities to which the T assets acquired by S are subject, and
      2. (ii)The fair market value of any consideration not provided by P pursuant to the plan of reorganization.
   2. (2)Reverse triangular merger. If P adjusts its basis in the T stock acquired as a result of a reverse triangular merger under § 1.358-6 (c)(2)(i) and (d), § 1.358-6 (c)(1)(ii) and (d)(2) do not apply. Instead, P adjusts such basis by taking into account the full amount of—
      1. (i)T liabilities deemed assumed by S or the amount of liabilities to which the T assets deemed acquired by S are subject, and
      2. (ii)The fair market value of any consideration not provided by P pursuant to the plan of reorganization.
   3. (3)Excess loss accounts. Negative adjustments under this section may exceed P's basis in its S or T stock. The resulting negative amount is P's excess loss account in its S or T stock. See § 1.1502-19 for rules treating excess loss accounts as negative basis, and treating references to stock basis as including references to excess loss accounts.
   4. (4)Application of other rules of law. If a transaction otherwise subject to this section is also a group structure change subject to § 1.1502-31, the provisions of § 1.1502-31 and not this section apply to determine stock basis. See § 1.1502-80(a) regarding the general applicability of other rules of law and a limitation on duplicative adjustments. See § 1.1502-80(d) for the non-application of section 357(c) to P.
   5. (5)Examples. The rules of this paragraph (b) are illustrated by the following examples. For purposes of these examples, P, S, and T are domestic corporations, P and S file consolidated returns, P owns all of the only class of S stock, the P stock exchanged in the transaction satisfies the requirements of the applicable triangular reorganization provisions, the facts set forth the only corporate activity, and tax liabilities are disregarded.
3. (c)Effective/applicability date. This section applies to reorganizations occurring on or after December 21, 1995. However, paragraph (b)(4) of this section applies to reorganizations occurring on or after September 17, 2008.