We sent our check Express Mail ( cost $41). It had a guaranteed delivery date, but it didn't get to ETI on the date. I called Express Mail, and they said they would look into it. The check did arrive at ETI two days late, and I threw away the Express Mail receipt figuring I didn't need it anymore. Yesterday, I got a letter from Express Mail saying they aren't sure why they missed the arrival date but that I should staple the receipt to the enclosed form and they would refund my $41. Sigh.