Credits or refunds after period of limitation
(a) A refund of any portion of an internal revenue tax shall be considered erroneous and a credit of any such portion shall be considered void—
(1) Expiration of period for filing claim. If made after the expiration of the period of limitation for filing claim therefor, unless within such period claim was filed; or
(2) Disallowance of claim and expiration of period for filing action. In the case of a claim filed within the proper time and disallowed by the Director, if the credit or refund was made after the expiration of the period of limitation for filing an action unless within such period an action was begun by the taxpayer.
Credit after period of limitation
(b) Any credit against a liability in respect of any taxable year shall be void if any payment in respect of such liability would be considered an overpayment under section 1101(a) of this title.