(a) Notification required. In any case where a taxpayer applies for a credit or refund of taxes paid by it in respect of a taxable year for which the taxpayer was the consenting attorney-in-fact of a reciprocal making the election provided by section 826(a), such taxpayer shall give notice to its reciprocal for such taxable year, first, upon applying for the credit or refund; and again, within 10 days from the date on which a final determination is made that such credit or refund has been allowed or denied.

(b) Notice form. The notices required by this section shall include the name and address of the taxpayer and shall be signed by the taxpayer or its duly authorized representative. In addition, there shall be attached to and made a part of each first notice a concise statement of the claim upon which the application for refund or credit is based; and there shall be attached to and made a part of each second notice:

(1) A copy of the notification (if any) received by the taxpayer indicating that the credit or refund has been allowed; and

(2) A statement setting forth the amount of such credit or refund attributable to taxes paid by the taxpayer on income received from the reciprocal, and the computation by which such amount was determined.

(c) Manner of apportioning refund or credit. The taxpayer shall determine the amount of the refund or credit attributable to taxes paid on income received from its reciprocal by reallocating its income and expense items for the taxable year, with respect to which the refund or credit is allowed, in the manner provided by §§ 1.826-3 and 1.826-4 so as to reflect the adjustments (if any) in such items which resulted in the credit or refund of tax for the taxable year. The taxpayer shall then recompute the tax attributable to income received from its reciprocal for such taxable year in the manner provided by § 1.826-5. The district director may require such additional information as may be necessary in the circumstances to verify the computations required by this paragraph.