To prove you mailed something, use USPS Certified Mail for delivery confirmation with tracking and signature (if purchased), a Certificate of Mailing (PS Form 3817) for date-of-mailing evidence (no delivery proof), or a basic USPS retail receipt for a tracking number and date. For non-USPS, take a photo of the package at the counter, get a shipping receipt, or use services that provide digital proof of delivery. For USPS Mail Certified Mail: Provides a tracking number and electronic confirmation of delivery or an attempted delivery; a signature receipt (green card or electronic) offers strong proof. Certificate of Mailing (COM): Offers proof you presented the item to the USPS on a specific date (using PS Form 3817), but not of delivery or insurance. Retail Receipt: A basic receipt from the counter shows the date and tracking number, offering proof of mailing. For Other Carriers (FedEx, UPS, etc.) Tracking Number: Use the tracking number online to get delivery confirmation and proof of delivery (POD), often a signature. Photos: Take a clear photo of the package with the shipping label at the drop-off location or with a postal clerk. Shipping Receipt: Keep the physical receipt provided at the shipping counter. Other Methods Email: Use a service that provides proof of content and delivery for emails, like Registered Email (RML). Fax: A fax cover sheet serves as proof of transmission. Key Takeaway Proof of Mailing (Date Only): Certificate of Mailing (COM). Proof of Mailing Delivery: Certified Mail with Return Receipt, or tracking services. For legal advice, consult a professional. Certificate of Mailing - The Basics - FAQ | USPSWhat is a Certificate of Mailing? A Certificate Of Mailing provides evidence that you sent an item when you say you did. This offiUSPSWhat is Certified Mail how it works for USPS - Pitney BowesCertified Mail is how the USPS provides customers with proof of mailing. Its a special service that alerts senders, via electronPitney Bowes