I pay salespeople a salary plus commission and most of the salespeople work over forty hours. Am i required to pay overtime or because its commission I do not have to pay overtime? What does the law require us to do?

Need to know the relevant state. Generally, inside sales commission employees are entitled to overtime if their regular rate of pay does not exceed one and one-half times the applicable minimum wage for every hour worked in a workweek in which overtime hours are worked and they do not earn more than half their weekly income from bona fide commissions.
For example, under California law, employees who are paid by commissions are entitled to minimum wages and overtime pay unless they are exempted. The overtime exemption applies if the employee is an executive, administrative, or professional as defined by the law. The exemption also applies if the employee is an outside salesperson.