26 U.S.C. § 111: Recovery of tax benefit items

Gross income does not include income attributable to the recovery during the taxable year of any amount deducted in any prior taxable year to the extent such amount did not reduce the amount of tax imposed by this chapter. a credit was allowable with respect to any amount for any prior taxable year, and during the taxable year there is a downward price adjustment or similar adjustment, Paragraph (1) shall not apply to the extent that the credit allowable for the recovered amount did not reduce the amount of tax imposed by this chapter. This subsection shall not apply with respect to the credit determined under section 46 and the foreign tax credit. For purposes of this section, an increase in a carryover which has not expired before the beginning of the taxable year in which the recovery or adjustment takes place shall be treated as reducing tax imposed by this chapter. any excluded amount under subsection (a) allowed for the purposes of this subtitle (other than section 531 or section 541) shall be allowed whether or not such amount resulted in a reduction of the tax under section 531 or the tax under section 541 for the prior taxable year; and where any excluded amount under subsection (a) was not allowable as a deduction for the prior taxable year for purposes of this subtitle other than of section 531 or section 541 but was allowable for the same taxable year under section 531 or section 541, then such excluded amount shall be allowable if it did not result in a reduction of the tax under section 531 or the tax under section 541.