The origin and return addresses on each of your stores can sometimes be used by your carrier when creating labels, and can be customized per store.
How to edit your store's origin and return address
Visit your store settings and click your store's name.
In the Addresses panel, click the Edit Addresses button.
Enter the origin address details.
Tip: If you want separate return and destination addresses, just uncheck the "Same as origin address" option under the Return section
Amazon buy shipping return address
When using Amazon Buy Shipping, Amazon will not allow SKULabs or any other product to list separate origin and return addresses.
How do I put in a different shipping zip code for shipping?
SKULabs recommends creating a case even if it goes nowhere requesting the following of Amazon.
"My local post office is giving me trouble accepting packages because the Ship From ZIP code does not match their post code. I need to have my returns go to one address and my shipments originate from another address in order to resolve this. Using Amazon Buy Shipping I can only specify the ShipFrom address and am unable to override the return address to be a separate address. Can you please help me resolve this issue with my local post office? They don't get credit for the packages I ship using them when the labels are created incorrectly like this."