There are times when you may not be working but still have to be paid. Under federal law, your employer may be required to pay you for your time if you are on-call, traveling for business or even sleeping while at the workplace.
If you work in a place that requires a 24-hour shift, then you should be entitled to payment for your entire shift. For example, if you're a surgeon who is on-call and who has to sleep in the hospital while awaiting the next emergency, you should be compensated for the time you're required to be on the job, even if you're sleeping. The catch is if you have a specific 8-hour period in which you are not on-call and are provided sleeping quarters. In that case, the employer may be able to avoid paying you for the time when you're sleeping. Others who may be paid in this manner include ambulance drivers, guards and caregivers who work full-time.
If you work on an on-call basis, there may be restrictions on you. For instance, you may not be able to work during your time off while you await a call, may be required to stay within a short distance of the employer or could be prohibited from drinking alcohol. If you are required to be on-call, you should be paid regardless of whether or not you worked. There are a few exceptions, but on the whole, if you must abide by your employer's rules while you're away from the workplace, then you may be able to receive compensation.
Source: FindLaw, "Getting Paid for Not Working," accessed Oct. 19, 2017