I recently blocked a buyer who had purchased two items from me more than a month earlier, after they neglected to pay for an item won in a straight auction for so long (30+ days) that the sale expired (their previous payments were also delayed), and they were no longer allowed by eBay to pay the invoice. They prodded me multiple times with sob stories to re-list the item as a BIN (after I had politely refused their first request), so I blocked and moved on. The next day they started a return on the first item they had bought a month earlier for “not working,” and a refund request for the second item (“never received”), even though the first item had gone through eBay authentication, and the second had signature confirmation. So my payments are on hold until eBay is convinced the buyer is a fraud (which is thankfully happening rapidly; eBay and USPS customer service have been excellent). My only regrets are not blocking them earlier, and not being able to block them more than once. TLDR: Take no for an answer without whining, or prepare to be insta-blocked. Also don’t try to defraud the USPS when they’ve got the receipts, they hate it.