I sold stuff on eBay that can only be sent electronically through email. This is the comment I left at the bottom of the invoice when i had the the buyer pay me. Feel free to use it.
[QUOTE]
You warrant that this transaction is a COD(Cash On Delivery) transaction. Payment for the goods(insert here) has been made at the time of delivery. By paying this invoice, the buyer and seller both collectively agree that the buyer has received his goods. No warranty is expressed or implied. Sold