The United States Postal Service Domestic Return Receipt Form is used as an evidence of delivery. The mailer gets this return receipt by first-class mail once the item is delivered. Date of delivery, recipient’s signature, and delivery address is provided in the Return Receipt. Sometimes, this return receipt is referred as “Green Gard.”
PS Form 3811 is used as USPS return receipt form (domestic). The receipt approved by USPS includes a tracking number which is also helpful, but that tracking number won’t help you to track the mail item sent by the mailer. Also, this receipt can’t be viewed online by any customer.
PS Form 3811:
Images of return receipt form:
PS Form 3811 – PDF