If you don't add a tip to the credit receipt, the IRS will estimate a tip value for tax purposes. I don't know the exact amount, but I think it's around 10%.

If you don't add a tip to the credit receipt, the IRS will estimate a tip value for tax purposes. I don't know the exact amount, but I think it's around 10%. If you are intent upon helping service staff evade taxes, the optimal strategy would therefore be to put 10% on the receipt and drop the remainder on the table in cash. This also means that if you stiff your server and leave no tip, they are still getting taxed as though you left 10%. If you really want to be a jerk, be slightly less of a jerk by leaving a $0.01 tip on the receipt. This will also allow them to post it to outrage-fueled social media for a tiny bit of temporary fame. Most people aren't that invested into stigginit to da Man, or at least not just via their restaurant tips. You'd be better off paying cash for everything, no-receipt requested, and not involving the electronic point-of-sale till at all.