You can now specify payment terms for customers in the format of:
Invoices raised on or before the 16th of the month are due at the end of the following month, those raised after this are due at the end of the month after that.
For example, an invoice raised today (7th September) would be due 31 October 2021.
An invoice raised on the 17th September would be due 20th November 2021.
The date (16th of the month in this case) can be specified on a per-customer basis.