29 C.F.R. § 778.223

(a) Under the Act an employee must be compensated for all hours worked. As a general rule the term “hours worked” will include:

(1) All time during which an employee is required to be on duty or to be on the employer's premises or at a prescribed workplace; and

(2) All time during which an employee is suffered or permitted to work whether or not he is required to do so.

(b) Thus, working time is not limited to the hours spent in active productive labor, but includes time given by the employee to the employer even though part of the time may be spent in idleness. Some of the hours spent by employees, under certain circumstances, in such activities as waiting for work, remaining “on call”, traveling on the employer's business or to and from workplaces, and in meal periods and rest periods are regarded as working time and some are not. The governing principles are discussed in part 785 of this chapter (interpretative bulletin on “hours worked”) and part 790 of this chapter (statement of effect of Portal-to-Portal Act of 1947). To the extent that these hours are regarded as working time, payment made as compensation for these hours obviously cannot be characterized as “payments not for hours worked.” Such compensation is treated in the same manner as compensation for any other working time and is, of course, included in the regular rate of pay. Where payment is ostensibly made as compensation for such of these hours as are not regarded as working time under the Act, the payment is nevertheless included in the regular rate of pay unless it qualifies for exclusion from the regular rate as one of a type of “payments made for occasional periods when no work is performed due to failure of the employer to provide sufficient work, or other similar cause” as discussed in § 778.218 or is excludable on some other basis under section 7(e)(2). For example, an employment contract may provide that employees who are assigned to take calls for specific periods will receive a payment of $5 for each 8-hour period during which they are “on call” in addition to pay at their regular (or overtime) rate for hours actually spent in making calls. If the employees who are thus on call are not confined to their homes or to any particular place, but may come and go as they please, provided that they leave word where they may be reached, the hours spent “on call” are not considered as hours worked. Although the payment received by such employees for such “on call” time is, therefore, not allocable to any specific hours of work, it is clearly paid as compensation for performing a duty involved in the employee's job and is not of a type excludable under section 7(e)(2). The payment must therefore be included in the employee's regular rate in the same manner as any payment for services, such as an attendance bonus, which is not related to any specific hours of work. The principle in this paragraph (b) also applies when such “on call” pay is mandated by state or local law.