While it is permissible for an employer and an employee to agree
upon different base rates of pay for different types of work, it is
settled under the Act that where a rate has been agreed upon as
applicable to a particular type of work the parties cannot lawfully
agree that the rate for that work shall be lower merely because the work
is performed during the statutory overtime hours, or during a week in
which statutory overtime is worked. Since a lower rate cannot lawfully
be set for overtime hours it is obvious that the parties cannot lawfully
agree that the working time will not be paid for at all. An agreement
that only the first 8 hours of work on any days or only the hours worked
between certain fixed hours of the day or only the first 40 hours of any
week will be counted as working time will clearly fail of its evasive
purpose. An announcement by
the employer that no overtime work will be permitted, or that overtime
work will not be compensated unless authorized in advance, will not
impair the employee's right to compensation for work which he is
actually suffered or permitted to perform.