Waiters like cash tips because they do not report the tips to the IRS and so keep all of the money. (Perhaps not all waiters, but the majority, per some web sites.) Tips put on a credit card are easier for the IRS to track.
I would like to make the waiters happy in this regard (esp since they are paid such low hourly wages, less than the usual minimum) but is there halacha that I should be considering?
Does it make a difference if I pay the restaurant bill with a credit card and leave the tip in cash versus paying both in cash? (I prefer to pay with credit card to get the points.)
Does it matter if the waiter is Jewish or not?