Gratuity and discounts

A gratuity should not be affected by a check or item discount. An example is if is check is $1000.00 and there is a 10% gratuity ,the Gratuity should be $100. If there is a 10 percent discount applied and the check goes to 900.00 the gratuity should stay at $100.00 and not go down to $90.00. Discounts should not affect gratuity