Assuming lists are in column A & B, try this for a list of a/c nos. compiled
from B that also appear in column A.
Assume row 1 has headings then in C2 enter:
=IF(A2="","",IF(ISNUMBER(MATCH(A2,B:B,0)),"",ROW() ))
in D2 enter:
=IF(ROWS($1:1)COUNT(C:C),"",INDEX(A:A,SMALL(C:C,R OWS($1:1))))
Copy both C & D down to the bottom of your list.
Hide column C and D will contain the list you require.
Hope this helps

"kix" wrote:

I have two columns 1st column has certain account numbers, the 2nd has those
same numbers plus a couple hundred more. I want to eliminate the account
numbers in 2nd column that do not exist in 1st column. I don't know how to
write a
formula for this.

Thank you.