26 CFR §1.1374-5

1. (a)In general. The loss carryforwards allowed as deductions against net recognized built-in gain under section 1374(b)(2) are allowed only to the extent their use is allowed under the rules applying to C corporations. Any other loss carryforwards, such as charitable contribution carryforwards under section 170(d)(2), are not allowed as deductions against net recognized built-in gain.
2. (b)Example. The rules of this section are illustrated by the following example.