I think it really depends on what the big picture looks like. First and foremost, make sure that the law is being followed. Generally, the salon must guarantee that you are paid minimum wage plus tips for all hours worked.
If I’m understanding the situation, you would be doing the manicure and a free add-on service. I’m assuming that the add-on is not something where you really schedule a bigger time slot, just something that can usually be added at the last minute. If so, then generally I would say that commission should only be paid on actual revenue generated. Since add-ons are typically fairly quick and lower in price, you will likely make up for the lost commission with a bigger tip and generate goodwill from the client. If the free service is something booked separately that requires significant time, then I would say the real question is whether the owner actually has a profitable plan in place.
In my studio I have reward points that allow my clients to get their art add-on free at every third appointment or so. As a salon owner I wouldn’t pay out commission on the free add-on, but it would count toward total revenue and calculating commission percentage, as I have a sliding scale that rewards productive techs.
— Candice Everest is owner of Panache Nail Studio in Stanwood, Wash.