We charge 6% on parts & labor with a cap of $28.71. We have a small list of items we do not charge ss on such as lof’s, bulb replacement, air filters because we do not want to draw attention to ss fees on petty items. Most of our competitors charge 8% with one I now of charging 12%. (Wow). I’ve heard people say “nobody ever complains about it” but those are the people that probably just never came back and you never knew it.