26 U.S. Code § 909 - Suspension of taxes and credits until related income taken into account
If there is a foreign tax credit splitting event with respect to a foreign income tax paid or accrued by the taxpayer, such tax shall not be taken into account for purposes of this title before the taxable year in which the related income is taken into account under this chapter by the taxpayer.
In the case of any foreign income tax not taken into account by reason of subsection (a) or (b), except as otherwise provided by the Secretary, such tax shall be so taken into account in the taxable year referred to in such subsection (other than for purposes of section 986(a)) as a foreign income tax paid or accrued in such taxable year.
There is a foreign tax credit splitting event with respect to a foreign income tax if the related income is (or will be) taken into account under this chapter by a covered person.
The term “foreign income tax” means any income, war profits, or excess profits tax paid or accrued to any foreign country or to any possession of the United States.
The term “related income” means, with respect to any portion of any foreign income tax, the income (or, as appropriate, earnings and profits) to which such portion of foreign income tax relates.