Form 940 definition including break down of areas in the definition. Analyzing the definition of key term often provides more insight about concepts. Form 940 can be defined as: IRS form used to report an employer’s federal unemployment taxes (FUTA) on an annual filing basis. Form 940 if a reporting form to report the payroll tax of FUTA. FUTA is a tax that the employer pays, a payroll tax that is not withheld from the employee wages.