Usually, when you make a best offer on an item, and if the seller accepts it, you’re obliged to complete the order. However, you can retract your offer if you accidently entered a wrong offer amount or the description of the item has changed significantly. You’ll need to fill out the Best Offer Cancellation form and select your reason for cancelling.
Best offers expire after 48 hours. If the seller hasn’t accepted yours by then, it’ll be declined automatically.
If the seller has accepted your offer but you still want to retract it, you should email them and ask if they can cancel the transaction.