JaneD, thank you for your reply. After I posted my query I did manage to set up a Payment Term as you have described. This will work across most months of the year but doesn't seem to work for dates in January and February.

As far as Quickbooks is concerned, 30 Days after the end of January 2020 is 1st March 2020 (February 2020 is a leap year) and 30 Days after the end of February 2020 is 1st April.

It would be better if Quickbooks could handle the payment terms with reference to the Calendar rather than specific dates.