Pay a Flat Fee is a term used to describe a situation in which a person pays a fixed amount for a service or product. This type of payment is often used when renting an apartment, car, or other item. The term can also be used to describe a situation in which a person pays a set fee for a service such as a lawyer or accountant. Paying a flat fee is often seen as a more cost-effective way to pay for services or products than paying by the hour or per unit.