Welcome!

IFERROR

The formula underlined works perfectly when there is a date in the relevent cell. When their is no date (data) it returns a error.

Ive had a go at trying to figure it out below.

=DATE(YEAR([Invoiced Date]2), MONTH([Invoiced Date]2) + 1, 20)

=DATE(YEAR,IFERROR([Invoiced Date]3),""), MONTH,IFERROR([Invoiced Date]3),"-"), + 1, 20)

Does checking to see if it is a date first get you there?

=If(ISDATE([Invoiced Date]2), DATE(YEAR([Invoiced Date]2), MONTH([Invoiced Date]2) + 1, 20), "")

Another option. Wrap the entire expression in IFERROR.

=IFERROR(DATE(YEAR([Invoiced Date]3), MONTH([Invoiced Date]3) + 1, 20), "")

Brett and John,

Thanks both for your insights. Working like treat.