You're eligible for a fee refund if you've refunded a buyer in full for a transaction made on Grailed.
Fee refunds are automatically sent when you refund the original transaction. Listings sold with a PayPal-connected account will automatically have the fee refunded as shown by the "Partner Commission Reversal" in the transaction detail page, once the refund to the buyer is completed.
Please note that if a sale is refunded as the result of a lost claim, the seller is ineligible for a fee refund and PayPal will not allow the fees to be refunded. Partial refunds are not eligible for fee refunds.
As of October 11, 2019, PayPal no longer returns its portion of the fees when a sale is refunded. For more information, please find their policy here.