For most returns, Guess typically requires a receipt or proof of purchase to process the return effectively. This is because the receipt serves as verification of the transaction and helps ensure that the item was purchased from an authorized Guess retailer. Without a receipt, the return may be subject to store policies which could vary. Generally, if you no longer have the receipt, Guess may offer you store credit or an exchange, but this ultimately depends on the specific return policy in place at the location where the purchase was made. It is always a good idea to check the current return policy on the official Guess website to get the most accurate and up-to-date information regarding return procedures and requirements.