Did you read the bit of Mike's message where he said:
"This requires the analysis addin so Tools|addins and check it" ?
--
David Biddulph

"Joe" wrote in message
...
....
I have tried your formula but i get #Name? error

"Mike H" wrote:

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.

"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