Joe,

With the date the invoice is raised in A1 put this in another cell

=EOMONTH(A1,0)+30 Format as date

This requires the analysis addin so Tools|addins and check it and it will
return a date 30 days from the end of the month the invoice was created.

Mike

"Joe" wrote:

Hi there. I would like to create a formula that calculates the days that the
invoice is outstanding. Now I have
=Today()
Date invoice plus 30 days
However, the 30 days should count after the end of the month of when the
invoice is raised. Any ideas? Thanks