If you’ve chosen to include Label Messages in your Printing Setup, it helps to know where the message will appear on the FedEx shipping label. For information on how to include these Label Messages (for example, an Order Number, SKU, or custom message) please visit this article.
On most FedEx shipping labels, there are three available fields in which you can insert a label message. The fields are labeled REF, INV, and PO, and they correspond to Label Messages #1, #2, and #3, respectively.
On FedEx Commercial invoices, Message #2 appears in the Special Instructions portion on the bottom left, and Message #3 appears under Purchase Order No. at the top right of the document.
Label Message 3 appears in the upper left corner:
Label Message 2 appears on the Special Instructions section: