I agree completely with all of those who have opined that you cannot take a tax deduction for the donation of the miles. Although tax is not my specialty, I have read several reports on this, and all of the reasoning discussed above is relevant. As noted, if any miles were earned on corporate-paid travel, the IRS will consider that you have incurred no personal cost to accrue the miles, therefore have no cost basis, and are giving away something that cost you nothing. Don't know of any reported case law on the subject, though.