Use this formula in cell B3:

=IF(COUNTIF(C$3:C3, C3)=2, 1, 0)
Let me know if it works.

"noelle" wrote:

I have a list of records that have many duplicates. I need a formula that I
can use in the adjacent column to show a 1 for the first instance of a
duplicate and a 0 for any others. The list is sorted so all dupes are
together.