"Recently finalized rules from the United States Postal Service seek to clarify that the date on a postmark does not 'necessarily represent either the place at which, or the date on which, the Postal Service first accepted possession of the mailpiece' ... [T]axpayers filing tax returns and other tax documents by traditional first-class mail, and to which a filing deadline applies, should adjust by mailing the document earlier, requesting and obtaining a manual postmark at a retail counter at the time of mailing, and/or obtaining a certificate of mailing at such time. Failing to do so runs the risk that a return, payment, or other document that is timely turned over to USPS will be postmarked after the filing or due date, with associated and sometimes significant financial consequences. "  MORE >>