What employees need to know about their rights.

Suffer or Permit to Work
The FLSA defines the term “employ” to include the words “suffer or permit to work”. Suffer or permit to work means that if an employer requires or allows employees to work, the time spent is generally hours worked.
Thus, time spent doing work not requested by the employer, but still allowed, is generally hours worked, since the employer knows or has reason to believe that the employees are continuing to work and the employer is benefiting from the work being done. This time is commonly referred to as “working off the clock.” If you would like to review an example of suffer or permit to work, please click here.
Rework
When an employee must correct mistakes in his or her work, the time must be treated as hours worked. The correction of errors, or “rework”, is hours worked, even when the employee voluntarily does the rework.
Waiting for Work
Time which an employee is required to be at work or allowed to work for his or her employer is hours worked. A person hired to do nothing or to do nothing but wait for something to do or something to happen is still working. The Supreme Court has stated that employees subject to the FLSA must be paid for all the time spent in “physical or mental exertion (whether burdensome or not) controlled or required by the employer and pursued necessarily and primarily for the benefit of the employer of his business.”
Place of Work
Hours worked include all the time during which an employee is required or allowed to perform work for an employer, regardless of where the work is done, whether on the employer’s premises, at a designated work place, at home or at some other location.
It is the duty of management to exercise control and see that work is not performed if the employer does not want it to be performed. An employer cannot sit back and accept the benefits of an employee’s work without considering the time spent to be hours worked. Merely making a rule against such work is not enough. The employer has the power to enforce the rule and must make every effort to do so. Employees generally may not volunteer to perform work without the employer having to count the time as hours worked.

http://www.dol.gov/elaws/esa/flsa/hoursworked/screen1d.asp