Payment terms creation with Fixed day and Additional Months

Hello - We have the Payment terms created as per our Business process, using Fixed day option in OBB8. WJe created 25FM = Fixed day 25 and Additional Month 1. If invoice is created in May= Due date is June 25, which is working as expected.

But Business is asking that if Invoice is created before 25, Due should be June 25.

If invoice is created between 26 - 31, It should be July 25. Posting the invoice after 25th, Business is getting one month extra.

Can you please let us know, if how this can be achieved.

Thanks