The broker of the aircraft I'm purchasing does not put the purchase price in the Bill of Sales. Here's what he uses:

"The standard entry on the BOS is "$1 & OVC" which means you purchased the aircraft for "$1.00 & other values considered" It is no ones business how much you paid for the aircraft. That's why we use this method.The bill of sale ,once registered, is a public document & can be looked up by anyone."

Not such a horrible idea, but if he does that, how do I prove what I paid for it when sending in my MD Use Tax???