Antonym of GRATUITY

Gratuity : a sum of money paid to an employee at the end of a period of employment.
Annuity : a fixed sum of money paid to someone each year, typically for the rest of their life.
Stipend : a fixed regular sum paid as a salary or as expenses to a clergyman, teacher, or public official.
Discount : a deduction from the usual cost of something.
Wages : a fixed regular payment earned for work or services, typically paid on a daily or weekly basis.

Antonym of Gratuity is Wages