Are you asking as a buyer, or as a seller?
If a buyer has not received his purchase within a few days past its last estimated delivery date, and there is no tracking showing delivery, that buyer has 30 days to open an item not received case with eBay.
If you're asking as a seller, and a buyer has opened such a case or has reported to you that his item has not yet been received, you are going to have to refund him, unless there is tracking showing delivery. In that case, you would explain that to the buyer and tell him to double check with the carrier whose employee marked it as having been delivered.
