29 CFR § 778.331 - Awards for performance on the job.
Where a prize is awarded for the quality, quantity or efficiency of work done by the employee during his customary working hours at his normal assigned tasks (whether on the employer's premises or elsewhere) it is obviously paid as additional remuneration for employment. Thus prizes paid for cooperation, courtesy, efficiency, highest production, best attendance, best quality of work, greatest number of overtime hours worked, etc., are part of the regular rate of pay. If the prize is paid in cash, the amount paid must be allocated (for the method of allocation see § 778.209) over the period during which it was earned to determine the resultant increase in the average hourly rate for each week of the period. If the prize is merchandise, the cost to the employer is the sum which must be allocated. Where the prize is either cash or merchandise, with the choice left the employee, the amount to be allocated is the amount (or the cost) of the actual prize he accepts.