29 C.F.R. § 779.417

(a) Whether compensation representing commissions constitutes most of an employee's pay, so as to satisfy the exemption condition contained in clause (2) or section 7(i), must be determined by testing the employee's compensation for a “representative period” of not less than 1 month. The Act does not define a representative period, but plainly contemplates a period which can reasonably be accepted by the employer, the employee, and disinterested persons as being truly representative of the compensation aspects of the employee's employment on which this exemption test depends. A representative period within the meaning of this exemption may be described generally as a period which typifies the total characteristics of an employee's earning pattern in his current employment situation, with respect to the fluctuations of the proportion of his commission earnings to his total compensation.

(b) To this end the period must be as recent a period, of sufficient length (see paragraph (c) of this section) to fully and fairly reflect all such factors, as can practicably be used. Thus, as a general rule, if a month is long enough to reflect the necessary factors, the most recent month for which necessary computations can be made prior to the payday for the first workweek in the current month should be chosen. Similarly, if it is necessary to use a period as long as a calendar or fiscal quarter year to fully represent such factors, the quarterly period used should ordinarily be the one ending immediately prior to the quarter in which the current workweek falls. If a period longer than a quarter year is required in order to include all the factors necessary to make it fully and fairly representative of the current period of employment for purposes of section 7(i), the end of such period should likewise be at least as recent as the end of the quarter year immediately preceding the quarter in which the current workweek falls. Thus, in the case of a representative period of 6 months or of 1 year, recomputation each quarter would be required so as to include in it the most recent two quarter-years or four quarter-years, as the case may be. The quarterly recomputation would tend to insure that the period used reflects any gradual changes in the characteristics of the employment which could be important in determining the ratio between compensation representing commissions and other compensation in the current employment situation of the employee.

(c) The representative period for determining whether more than half of an employee's compensation represents commissions cannot, under the express terms of section 7(i), be less than 1 month. The period chosen should be long enough to stabilize the measure of the balance between the portions of the employee's compensation which respectively represent commissions and other earnings, against purely seasonal or plainly temporary changes. Although the Act sets no upper limit on the length of the period, the statutory intent would not appear to be served by any recognition of a period in excess of 1 year as representative for purposes of this exemption. There would seem to be no employment situation in a retail or service establishment in which a period longer than a year would be needed to represent the seasonal and other fluctuations in commission compensation.

(d) Accordingly, for each employee whose exemption is to be tested in any workweek under clause (2) of section 7(i), an appropriate representative period or a formula for establishing such a period must be chosen and must be designated and substantiated in the employer's records (see § 516.16 of this chapter). When the facts change so that the designated period or the period established by the designated formula is no longer representative, a new representative period or formula therefor must be adopted which is appropriate and sufficient for the purpose, and designated and substantiated in the employer's records. Although the period selected and designated must be one which is representative with respect to the particular employee for whom exemption is sought, and the appropriateness of the representative period for that employee will always depend on his individual earning pattern, there may be situations in which the factors affecting the proportionate relationship between total compensation and compensation representing commissions will be substantially identical for a group or groups of employees in a particular occupation or department of a retail or service establishment or in the establishment as a whole. Where this can be demonstrated to be a fact, and is substantiated by pertinent information in the employer's records, the same representative period or formula for establishing such a period may properly be used for each of the similarly situated employees in the group.