As long as an eBay category supports the feature, sellers have the option of enabling the Best Offer feature for a listing. The Best Offer feature enables a buyer to make a lower-priced offer on that item.
Note: Best Offer is not available for multi-variation listings.
If the seller receives a Best Offer from a prospective buyer, that seller can either accept or reject the Best Offer, or submit a counteroffer to that prospective buyer. If the seller does not act on the received Best Offer, the Best Offer will naturally expire after 48 hours.
A buyer is alerted when making the final Best Offer allowed for an item, but a buyer is not told how many Best Offers are permitted for items in the category. This is intentional, to discourage buyers from making less-than-serious Best Offers for an item. A BestOfferPlaced notification is created when a buyer makes a Best Offer on an item. Refer to BestOfferPlaced Notification for additional information.
If a Best Offer does not meet the seller's minimum acceptance price, the seller can decline the Best Offer or submit a counteroffer. The seller can use the RespondToBestOffer call to accept or decline a Best Offer, or to make a counteroffer.
Offers declined by the seller, retracted by the buyer, or allowed to expire count against the buyer's maximum number of Best Offers allowed per item, per marketplace.
For additional information about using the Best Offer feature, refer to Adding Best Offer to your listing and sending offers to buyers.