General rule
(a) If any claim, statement, or other document (other than a return or other document required under authority of chapter 21 of this title), required to be filed within a prescribed period or on or before a prescribed date under authority of any provision of the internal revenue laws is, after such period or such date, delivered by United States mail to the agency, officer, or office with which such claim, statement, or other document is required to be filed, the date of the United States postmark stamped on the cover in which such claim, statement, or other document is mailed shall be deemed to be the date of delivery. This subsection shall apply only if the postmark date falls within the prescribed period or on or before the prescribed date for the filing of the claim, statement, or other document, determined with regard to any extension granted for such filing, and only if the claim, statement, or other document was, within the prescribed time, deposited in the United States mail in an envelope or other appropriate wrapper, postage prepaid, properly addressed to the agency, office, or officer with which the claim, statement, or other document is required to be filed.
Stamp machine
(b) This section shall apply in the case of postmarks not made by the United States Post Office only if and to the extent provided by regulations prescribed by the Director.
Registered mail
(c) If any such claim, statement or other document is sent by United States registered mail, such registration shall be prima facie evidence that the claim, statement or other document was delivered to the agency, office or officer to which addressed, and the date of registration shall be deemed the postmark date.
Exception
(d) This section shall not apply with respect to the filing of a document in any court.