On some ebay buy it now listings you may notice a button directly under the buy it now button which says "make offer". When a seller places a buy it now listing they have the option of considering and accepting a potential buyers best offer for that item. As a buyer this gives you the opportunity to barter with the seller. You may possibly get a better deal on the item if the seller finds your offer accpetable.
When placing an offer there are a few things to consider. These are outlined below.
1. If your offer is accepted then you MUST purchase the item. The same rules apply for an accepted best offer as they do if you won an item in the "normal" way by being the highest bidder. It's a lot of hassle for sellers (especially high volume ones) to chase up non paying bidders. As soon as an item ends ebay take fees from a seller so if an item is not paid for a seller must claim those fees back which means opening a dispute with ebay. This could also lead to you as a buyer receiving negative feedback and an unpaid item strike from ebay.
2. When considering how much you want to offer for an item make your 1st offer your very best offer. You cannot barter back and forward for all items so you will only get to make 1 offer per listing. This can also save time and shows the seller you are serious about buying and your offer is more likely to be accepted straight away.
3. Don't make ridiculously low offers. They have absolutley zero chance of being accepted. If someone is selling an item on buy it now for say £49.99 and you offer £19.99 it is never going to be accepted. If you really want the item make a serious offer and chances are it will be accepted and you will make a nice saving. Put yourself in the sellers shoes and before you offer ask yourself, if you were selling something would you take half or less than half of the asking price. A good rule of thumb is to aim for a 5-20% discount. If an item already seems like a fairly good deal then chances are the seller has already priced it to sell. In that case aim for a smaller percentage discount.