USPS 421 Retail Clerk Practice Exam 2025 - Free Retail Clerk Practice Questions and Study Guide

The form that serves as proof of mailing for Certified Mail is PS Form 3800. This form is specifically designed for customers to use when sending Certified Mail, and it provides a receipt that confirms the item was mailed. Additionally, PS Form 3800 includes a tracking barcode, which allows both the sender and the recipient to monitor the status of the mailpiece as it moves through the postal system.

This form not only acts as proof of mailing but also confirms that it was sent with the certified service, which includes important features like a return receipt option and extra security. The receipt issued upon mailing can be retained by the sender for their records to verify that the item was mailed and to track its delivery.

In contrast, the other forms listed serve different purposes within the postal service. For example, PS Form 3820 is used for the application for Business Reply Mail, while PS Form 3813 is intended for certain types of return receipts, and PS Form 3816 is related to delivery confirmation. Thus, PS Form 3800 is clearly the correct choice for proving Certified Mail was sent.