Working off the clock refers to any time you perform your job duties while you are not being paid. It may seem like no big deal on an individual level, you have this work you need to finish, and you just need it done. But generally, it is illegal under the Fair Labor Standards Act. In a perfect world, the rules would morph and work for every situation, but this isn’t a perfect world, and so the rules need to be broadly drafted to protect against abuse.
The FLSA has strict rules mandating that any work that is unpaid is illegal. It requires that work beyond the 40 hour maximum, except in some narrow circumstances, must be paid as overtime. Sometimes it is hard to tell if what you are doing is really “off the clock.”
For example, sometimes workers are required to do preparatory tasks before starting to perform their primary functions. But if you engage in such activities as setting up a restaurant, preparing a worksite or warming up a vehicle, then you must be paid for the time spent on these tasks. Similarly, if you are required to do any post-shift tasks like cleaning or paperwork, then you must be paid. Basically, anything that you are required to do by your employer is work for which you should be paid.
If you believe that you performed some off the clock work, then you may want to sit down and speak with an employment attorney. These claims can be complicated, especially in proving how much time you spent on a given task, and an attorney can help clarify your legal rights. It is good to have a strong work ethic, but that ethic should also apply to your boss. You worked, therefore, you should be paid.