Get Post Office Retail Counter Employee to Manually Postmark, or "hand-cancel" Item For Accurate Postmark
From the article: "...Note: If you wish to have your mail postmarked for the purpose of indicating the exact date it was submitted for mailing, you can go to any USPS retail counter and request a postal employee to manually postmark, or "hand-cancel", up to 50 items for free. If you wish to have more than 50 items hand-canceled, please contact the local Postmaster or other manager in advance to ensure adequate resources are available to assist. ..."
Article Reference: usps.com
