On Feb 5, 1:59*pm, Dave wrote:
I have a formula to return a monthly salary in a budgeting sheet. *It
compares three dates; a startdate (in K3), when the person started
work, the date at the end of a month(in V2), and a leavedate when they
left employment(in K3). *It has to give "NS" (not started) in any
month before they were employed, their budgeted salary
(ROUND($O3/12,1) for each month employed, and "left" for any month
that they are no longer employed.
[....]
= IF($K3="",IF($J3<$V$2,ROUND($O3/12,1),"NS"),IF($K3$V
$2,ROUND($O3/12,1),"left"))

I think you have the right idea. The problem is likely the extra
parenthesis after "NS". But I did not study your formula to see if
its logic fits your requirement. I think it can be simplified.
Assuming that J3, not K3, is the starting date, try:

=if(V2<$J3, "NS", if(or($K3="",V2<=$K3), round($O3/12,1), "left"))