If you return an item purchased with your Vestiaire Collective discount code, you'll receive Store Credit for the portion of the price covered by the code.
Specifically, you'll receive Store Credit equal to the value of your returned item(s) if this value is less than your original discount code amount. Otherwise, the Store Credit will be for the full original value of the code.
Any remaining amount you paid for the order (beyond the discount) will be refunded to the payment method you originally used.