29 CFR § 778.114 - Fixed salary for fluctuating hours.
(a) An employee employed on a salary basis may have hours of work which fluctuate from week to week and the salary may be paid him pursuant to an understanding with his employer that he will receive such fixed amount as straight time pay for whatever hours he is called upon to work in a workweek, whether few or many. Where there is a clear mutual understanding of the parties that the fixed salary is compensation (apart from overtime premiums) for the hours worked each workweek, whatever their number, rather than for working 40 hours or some other fixed weekly work period, such a salary arrangement is permitted by the Act if the amount of the salary is sufficient to provide compensation to the employee at a rate not less than the applicable minimum wage rate for every hour worked in those workweeks in which the number of hours he works is greatest, and if he receives extra compensation, in addition to such salary, for all overtime hours worked at a rate not less than one-half his regular rate of pay. Since the salary in such a situation is intended to compensate the employee at straight time rates for whatever hours are worked in the workweek, the regular rate of the employee will vary from week to week and is determined by dividing the number of hours worked in the workweek into the amount of the salary to obtain the applicable hourly rate for the week. Payment for overtime hours at one-half such rate in addition to the salary satisfies the overtime pay requirement because such hours have already been compensated at the straight time regular rate, under the salary arrangement.
(b) The application of the principles above stated may be illustrated by the case of an employee whose hours of work do not customarily follow a regular schedule but vary from week to week, whose total weekly hours of work never exceed 50 hours in a workweek, and whose salary of $600 a week is paid with the understanding that it constitutes the employee's compensation, except for overtime premiums, for whatever hours are worked in the workweek. If during the course of 4 weeks this employee works 40, 37.5, 50, and 48 hours, the regular hourly rate of pay in each of these weeks is $15.00, $16.00, $12.00, and $12.50, respectively. Since the employee has already received straight-time compensation on a salary basis for all hours worked, only additional half-time pay is due. For the first week the employee is entitled to be paid $600; for the second week $600.00; for the third week $660 ($600 plus 10 hours at $6.00 or 40 hours at $12.00 plus 10 hours at $18.00); for the fourth week $650 ($600 plus 8 hours at $6.25, or 40 hours at $12.50 plus 8 hours at $18.75).
(c) The “fluctuating workweek” method of overtime payment may not be used unless the salary is sufficiently large to assure that no workweek will be worked in which the employee's average hourly earnings from the salary fall below the minimum hourly wage rate applicable under the Act, and unless the employee clearly understands that the salary covers whatever hours the job may demand in a particular workweek and the employer pays the salary even though the workweek is one in which a full schedule of hours is not worked. Typically, such salaries are paid to employees who do not customarily work a regular schedule of hours and are in amounts agreed on by the parties as adequate straight-time compensation for long workweeks as well as short ones, under the circumstances of the employment as a whole. Where all the legal prerequisites for use of the “fluctuating workweek” method of overtime payment are present, the Act, in requiring that “not less than” the prescribed premium of 50 percent for overtime hours worked be paid, does not prohibit paying more. On the other hand, where all the facts indicate that an employee is being paid for his overtime hours at a rate no greater than that which he receives for nonovertime hours, compliance with the Act cannot be rested on any application of the fluctuating workweek overtime formula.