I looked at a catering proposal for a friend last Tuesday. The document said the dinner was eighty dollars per person. There were two small plus signs printed directly next to the number. That means plus tax and plus service charge.
My friend thought the service charge was the tip for the waiters. It almost never is. The service charge usually goes straight to the venue to pay for their internal administrative costs. It is typically around twenty percent of your total food and beverage minimum. Then the state taxes both the food and that service charge. Then you still have to tip the actual bartending and wait staff at the end of the night.
Her eighty dollar dinner was actually closer to one hundred and ten dollars a plate before anyone even poured a glass of water.
You have to ask the venue exactly what their service fee covers before you sign the paper. Get the answer in an email so you have a written record. If you do not ask, you will end up owing thousands of extra dollars on the final invoice thirty days before your wedding. Do not assume the venue is handling the gratuity just because they added a massive fee to the second page of the contract.