Hi Jorge,
Which option you have selected in customization whether Due Date As in Source Flow or Due Date As Entered?
The above options behave as described below
Due Date: Due Date As in Source Flow
The due date is determined according to the rule that is already set. SAP recommends that you set the "Move to Current Date" indicator, at least for follow-up postings. The result is that the due date is moved to the current date (the system date at the time of the change) if the due date is before this date.
Due Date As Entered
When follow-up postings result from a change to the contract, the system asks in the application dialog when these should be due. For all follow-up postings that are due before the date determined by the set rule, the system moves the due dates to this date.
P.S: If you create a Due date correction rule with out any name, system will pick up that rule by default ( Empty named rule behaves as default rule).
Thanks and Regards,
Chandra