His tax liability is a capital gain (ordinary tax rates instead of capital gain rates since he held it for less than 1 year) on selling the baseball for the tickets, boxes, etc. the Yankees gave him for it. If Jeter covers the taxes for him, they could argue that that was a gift from Jeter to him, but I suspect the IRS would take the position that was additional proceeds from selling the baseball and tax that as a capital gain (again ordinary rates). If they take the position that Jeter's reimbursing him for the taxes was a gift, then it's not taxable to the recipient, and also not taxable to Jeter to the extent the gift doesn't exceed $13,000. If the gift does exceed $13,000, he wouldn't have to pay any gift tax now unless he wanted to. He could elect to have it reducehis lifetime exclusion for estate tax purposes and let his estate pay it (hopefully a long time from now).