What is an "unpaid invoice"?
Your buyer receives an invoice at the end of the transaction.
If your buyer does not pay within four days, on the fifth day, you, the seller, can cancel, citing "buyer did not pay" as the reason. You CAN wait longer, but keep in mind that you have only 30 days to do this.
Again, can you explain what an "unpaid invoice" would be?
If you plan on sending the buyer a second invoice or a reminder of some kind, don't.
eBay does that. You need to use the tools eBay gives you to handle the transaction.
