Originally Posted by sfvoyage

Why is that necessary? Can't you just put the tip on the original bill and pay with your credit card? Or are you saying that if your total bill falls under your PP allowance, no bill is generated to begin with? (My experience was that my total exceeded my allowance, so I got a bill with a balance due of the difference, to which I added a tip of any amount I should choose and paid with my credit card.)