USPS Certified Mail is a service offered by the United States Postal Service (USPS) that provides proof of mailing and delivery for important or time-sensitive mail pieces. With Certified Mail, a recipient signature is required upon delivery, and the sender receives an electronic or physical certificate of mailing, which provides evidence that the mail piece was sent and delivered. USPS Certified Mail is often used for important legal, financial, or personal documents, such as court filings, contracts, or tax documents. The use of Certified Mail provides added security and peace of mind for the sender, as it ensures that the mail piece was delivered to the correct recipient and provides evidence of the date and time of delivery. USPS Certified Mail costs more than regular mail, but it provides added security and reliability for essential or time-sensitive mail pieces.