HR can an employer under any reason not pay OT???

Anything over 40 hours in a week must be paid as overtime unless you are an exempt employee (usually defined as a salaried employee). My guess is that if you continuously go over your 40 hours, you may see your hours cut to say 35 to 37 since you are violating their policy that you are not supposed to work overtime without pre-approval.

Overtime rules are handled by the U.S. Department of Labor, Employment Standards Administration, Wage and Hour Division - for more info, I would contact them direct (they should have an area office relatively near you - check http://www.dol.gov/esa and look for Wage and Hour.

They have a right to say no overtime, or no overtime unless authorized. Therefore, if you stay late, it's on your time, not theirs, and they do not have to pay you.

If they authorize overtime, they can pay you straight time up to 40 hours (if your normal work week is less) and then time and a half after 40 hours.

But if overtime isn't authorized, don't hang around hoping for a bigger check.

Basically, salaried employees don't get paid OT.

Most companies don't want to pay OT because it is expensive. That is why it must be approved in advanced.

If you work a lot of unapproved OT, they can/will fire you for it.

I think that ALL OT, whether approved or not, must be paid.

California Labour Law re: overtime

If they allow you to work OT, then they have to pay you for it. But don't be real surprised if you get fired for violating their rule on no OT.