=IFERROR(MATCH(A2,Sheet A!$A$2:$A$6,0),"Not in Sheet A")
Where A2 contains the Cost ID on Sheet 2 and SheetA!$A$2:$A$6 is the range
containing Cost ID on Sheet A. Adjust as needed.

"Mary" wrote:

Hi,
I have values on two sheets but sheet A is not complete I am trying to see
which ones are missing. Example:
Sheet A Sheet2 Result
1 Cost Id Cost Id
2 30252 30252
3 30254 30253 Not in Sheet A
4 30256 30254
5 30257 30255 Not in Sheet A
6 30279 30256
7 30257
8 30258 Not in Sheet A
9 30259 Not in Sheet A
10 30260 Not in Sheet A