Ancillary services endorsements, such as "Return Service Requested", are not able to be added to USPS labels in ShippingEasy at this time.
If you are shipping an package that requires this service endorsement, you may be able to hand-write the endorsement on the label. However, it is advisable to check with your local post office before doing so. Visit USPS for more information.
How to: Create a prepaid return label
What are the character limits for USPS labels?
Why didn't my logo print on my shipping label?
How to: Edit a label
Why is my order number not showing up on my label?