It is possible to unblock the SDD payment of one or more instalments so that they can be paid at any time, regardless of the due date set for the instalment payement.
From the Payment Window:
click on the padlock icon to unblock the instalment, so that it can be paid at any time rather than on the date specified
From the User Profile
1) click on the row of the item with an SDD payment, click on Accounting and click on Edit next to the instalment/s
2) select No to unblock the instalment and click on OK to save the changes