=DATEDIF(TODAY(),"12/31/"&YEAR(TODAY()),"m")
will give you the no. of completed months left from today.

You can replace today() with a date or refrence to a date (address of cell
containing a date)

"terryc" wrote:

Employee benefit period is 6/1-5/31. An employee pays 20% of our cost for
medical insurance. Since there may be 2 or 3 paychecks in a month, we divide
the annual cost by 26 paychecks per year.

Is there a function that recognizes 6/1, 7/1 etc so I could calculate how
many months remain in the benefit year* cost of insurance * 20%? Thanks.