The U.S. Postal Service (USPS) implemented new procedures for dating mail on Dec. 24, postmarking letters and packages with the date they are processed at a postal facility rather than when they are dropped off in a mailbox — a shift that could affect whether time-sensitive mail is considered on time.  The USPS says the change is aimed at meeting strategic goals to cut costs and streamline mail processing by concentrating it in a smaller number of facilities. But it could create real challenges for consumers dealing with deadline-driven mail matters this tax season and beyond, from IRS filings and Medicare documents to mail-in ballots and government benefit notices. Date differences between when a piece of mail is dropped off by the sender and when it is processed and postmarked are likely to “become more common” as the changes roll out, according to USPS. That means a tax return dropped in a big blue mailbox on April 15 or a vote-by-mail ballot sent on Election Day could still be marked late — risking IRS penalties or a rejected vote — because USPS now postmarks when mail is processed rather than when it is sent.  If you typically wait until the day before your tax deadline to mail your return, you might want to rethink simply slipping it into a mailbox or post office receptacle. Instead, consider taking it inside the post office and choosing one of these in-person options to document that it was in USPS’ hands ahead of a deadline: In many situations, you can submit timely paperwork online and eliminate worry about missing a mail-by date. Online filing typically provides clear, immediate proof of submission and bypasses the risk of processing delays at the post office. Examples include: Filing tax returns. Filing electronically through IRS e-file or authorized tax software such as TurboTax, TaxAct or H&R Block provides instant confirmation that your return was received, eliminating uncertainty caused by USPS processing. Social Security applications and forms. You can apply for retirement benefits, family benefits and Social Security Disability Insurance and digitally submit supporting documents using the My Social Security platform. Some forms, such as applications for survivor benefits, must be filed by phone or in person. Medicare paperwork. You can enroll in Medicare Parts A and B online through an online My Social Security account and, in some cases, join or switch Medicare Advantage or Medicare Part D drug plans via Medicare.gov. Level 3 Medicare appeals can be made through the U.S. Health and Human Services Department’s appeal portal. For mail-in voting, plan to send your ballot well in advance of Election Day. Or use options like drop boxes or hand delivery at election offices, based on your local rules. ​ Aaron Kassraie writes about issues important to military veterans and their families for AARP. He also serves as a general assignment reporter. Kassraie previously covered U.S. foreign policy as a correspondent for the Kuwait News Agency’s Washington bureau and worked in news gathering for USA Today and Al Jazeera English.​ ​ Unlock Access to AARP Members Edition Already a Member? Login