Explanation

This formula relies on a helper column, which is column E in the example shown.

Once this formula is in place, theCOUNTIFS functioncan be used to count new customers in each month.

As this formula is copied down, it returns the count of new customers in each month.

Excel formula: Customer is new

Use a positive value for months to move forward in time, and a negative number…

Excel formula: Summary count by month with COUNTIFS

Excel formula: Flag first duplicate in a list

Excel formula: Highlight duplicate values

Excel COUNTIFS function

Excel EOMONTH function