Quick answer
If the item you purchased arrived damaged or not as described, and you reported the issues to the seller or Reverb within 7 days of delivery, the seller would be responsible for the return shipping costs. On a preference-based return, typically the buyer would be responsible for purchasing the return shipping label, as well as coordinating return shipping logistics with the carrier.
Within the US, sellers can purchase return shipping labels directly via Reverb. For orders where a shipping label through Reverb is not available, the seller and buyer should work together to find the best avenue for return shipment.
If you would like to purchase a return shipping label through Reverb for your preference-based return, contact our support team so they can get this created and sent to you. In order to make this happen, be sure you have a shop profile set up with a billing card on file, and our team will add the return shipping label to your billing statement.
Further reading:
Refunds and returns for buyers
How do returns work for sellers on Reverb?
How can I request a refund or return?