29 C.F.R. § 778.307
Where deductions as described in § 778.304(a)(5) are made for disciplinary reasons, the regular rate of an employee is computed before deductions are made, as in the case of deductions of the types in paragraphs (a) (1), (2), and (3) of § 778.304 . Thus where disciplinary deductions are made from a piece-worker's earnings, the earnings at piece rates must be totaled and divided by the total hours worked to determine the regular rate before the deduction is applied. In no event may such deductions (or deductions of the type described in § 778.304(a)(2) ) reduce the earnings to an average below the applicable minimum wage or cut into any part of the overtime compensation due the employee. For a full discussion of the limits placed on such deductions, see part 531 of this chapter. The principles set forth therein with relation to deductions have no application, however, to situations involving refusal or failure to pay the full amount of wages due. See part 531 of this chapter; also § 778.306 . It should be noted that although an employer may penalize an employee for lateness subject to the limitations stated above by deducting a half hour's straight time pay from his wages, for example, for each half hour, or fraction thereof of his lateness, the employer must still count as hours worked all the time actually worked by the employee in determining the amount of overtime compensation due for the workweek.
29 C.F.R. §778.307