on 02-24-2013 06:17 PM
Unless you file an unpaid item dispute after a minimum of 4 days from end of auction, the buyer has 45 days to pay.
Therefor it would be a very good idea to file an unpaid item dispute right away, then if eBay can't collect for you within another 4 days you are free to relist and eBay will return the final value fees they charged your for that listing.
Sellers do not have to send an invoice to get paid, eBay does that for you at the end of the listing. You only need to send an invoice if there are modifications involved like international shipping charges or a combined invoice for multiple listings for which you want to reduce the total shipping charge.