I mean even if the exchange messed up and took out more tax than they should have, he would just fix that at tax filing time and get a refund. If the exchange

I mean even if the exchange messed up and took out more tax than they should have, he would just fix that at tax filing time and get a refund. If the exchange was overseas/super sketchy it's possible that the exchange just plain stole some of his money and claimed it was "for taxes."