The USPS assigns Mailer IDs based on mail volume. For mailers with an annual volume of fewer than 10 million pieces, a 9-digit ID will be assigned. If you mail more than 10 million pieces, you will have a 6-digit ID. The Serial Number/Piece ID field is one of the main differences between the Basic and Full IMB
If your lodge has an IMB, you can enter it into the system, and the system will print the barcode on the labels you print.
Click on Lodge Settings

Find Lodge Mailing Settings and click on Edit

Enter in the number provided by USPS and click on Save Lodge Information
