I have two spread sheets. One has employee benefits 09/12 and the other has
employee benefits 09/19. I want to compare the employee benefits and they
are not the same, return the diff.

Here is my formula
B2-(VLOOKUP($A2,'09-12'!$A$2:F$484,2))

It is working correctly for all but one. I have two people that I know
should have a different amount from the previous week and that difference is
showing up. I have three new hire on sheet 09/19 that were not on sheet
09/12.
For two of them it is returning 0's. For the other one it is returning an
amount.