(a) Period in which claim may be filed. In the case of an overpayment of income tax resulting from a credit, allowed under the provisions of section 901 or under the provisions of any treaty to which the United States is a party, for taxes paid or accrued to a foreign country or possession of the United States, a claim for credit or refund must be filed by the taxpayer within 10 years from the last date prescribed for filing the return (determined without regard to any extension of time for filing such return) for the taxable year with respect to which the claim is made. Such 10-year period shall be applied in lieu of the 3-year period prescribed in section 6511(a).

(b) Limit on amount to be credited or refunded. In the case of a claim described in paragraph (a) of this section, the amount of the credit or refund allowed or made may exceed the portion of the tax paid within the period prescribed in section 6511 (b) or (c), whichever is applicable, to the extent of the amount of the overpayment attributable to the allowance of a credit against income tax referred to in paragraph (a) of this section.