Most tax professionals are aware of the common-law “mailbox rule,” which provides that proof of proper mailing creates a rebuttable presumption that the document was physically delivered to the addressee. Internal Revenue Code (Code) section 7502 was enacted to codify the mailbox rule for tax purposes. Thus, for documents received after the applicable deadline, the document will be deemed to have been delivered on the date the document is postmarked. To protect taxpayers against a failure of delivery, Code section 7502 also provides that when a document is sent by registered mail, the registration serves as prima facie evidence that the document was delivered, and the date of registration is treated as the postmark date. In other words, if the Internal Revenue Service (IRS) claims not to have received a document, the presumption arises that such document was delivered so long as the taxpayer produces the registration.