What identifier is required when changing address information in a trademark application?

When changing address information in a trademark application, the required identifier is the serial or registration number. This number uniquely identifies a trademark application that has been submitted to the USPTO and is essential for any modifications or updates regarding the application. By using the serial or registration number, the USPTO can quickly locate the specific application to process the address change accurately.

The serial number is particularly critical because it ensures that the correct file is referenced, which is vital for maintaining the integrity of the trademark records and communications. Other identifiers, such as the client ID, trademark title, or application date, lack the specificity needed to pinpoint the exact application in question and may not be recognized by the USPTO for this purpose. Therefore, using the serial or registration number is the most effective and necessary step in making address changes to ensure compliance and proper administrative handling within the trademark system.