What must the exterior of a tax bill include if the United States Postal Service should return it if undeliverable?

The requirement for the exterior of a tax bill to include "RETURN SERVICE REQUESTED" is critical because this specific language instructs the United States Postal Service to return the mailpiece to the sender if it cannot be delivered to the intended recipient. This notation ensures that the sender receives notification of the undeliverable status of the tax bill, facilitating communication and allowing for updates or corrections of the recipient’s address.

This practice is particularly important in the context of property taxes. Municipalities need to ensure that tax bills reach property owners efficiently, as undelivered bills can lead to misunderstandings about tax obligations, potential penalties, and other administrative complications. By using "RETURN SERVICE REQUESTED," the sender can maintain accurate records and follow up on undelivered mail.

Other options do not possess the specific legal and procedural weight of "RETURN SERVICE REQUESTED," which may not effectively alert the sender of undeliverable mail or lack the clarity needed for postal processing. This highlights the importance of using formal and recognized language in mailing practices.