Are you a buyer who wants to secure the purchase of an item without paying the full amount straight away? Or a seller intending to offer a partial refund?
If you are the buyer then please be advised that split payments invalidate the eBay MBG if there is a problem with the item. Deposits do not guarantee you will win or have bought the item.
As a seller, the amount of a partial refund surely depends upon why you are refunding.
Have you discussed a partial refund with your buyer?
All refunds should be done through a case in the Resolution Centre:
https://resolutioncentre.ebay.co.uk/
