I am an exempt employee. My company permits us to take vacation in 4 hour allotments.  Requests for vacation are made in advance and approved.  Payroll is done every two weeks. Our week starts on a Monday and ends on Sunday for payroll purposes. All employees, even those of us who are exempt must clock in and out.  

On a given week, I requested and was approved for 8 hours of vacation.  As it worked out, do to my workload, I actually worked 40 hours in four days.  The HR person is telling me that although I worked 40 hours, I still need to take my 8 hours of vacation in order to take this Friday off.  I have been classified as an exempt employee for the past 25 years.  No other employer has ever asked me to take accrued vacation when I have already worked 40 hours in a given workweek.  BTW, I worked 40 hours the week before, so I am not short hours in the pay period. 

Is this legal?   The HR person is telling me that all exempt employees are expected to work more than 40 hours a week.  Typically I work 42-44 hours each week, because the work never ends.  Can a company require me to take vacation even when I have fulfilled my 40 hour requirement?

Thanks in advance for your reply.

Yes they can, vacation balances and usage are up to the employer's policy.  Some do look at how many other hours you work in a week and others do not.  If you were trying to work so as to not have to use a vacation day, it would have been better to ask beforehand.  The employer is allowed to set your schedule even if you are exempt and to state that if you miss 4 hours in any day, that you must use any vacation time you have accrued.

Nothing you posted goes against any federal laws, and no state laws that I know of, even California which tends to be the most pro-employee of states. 

The number of hours you have worked is actually irrelevant because you are an exempt employee.  Because the regulations permit employers to use hours for administrative purposes, particularly certain kinds of payroll functions, it can be confusing.  As an exempt employee, you are effectively paid by days of work not hours of work.  You want to take a day off.  That day is represented in payroll as 8 hours.

Managers often permit exempt employees to "make up" their hours, but that's not a solid practice because it can actually be used to show that the exempt employee was not exempt because what mattered was time worked, which is the big red flag that screams hourly basis of pay.  You are being treated fairly and properly.