Once a payment is recorded in the SMDU UI it cannot be deleted. If the payment needs to be deleted (i.e. if the payment was returned for non-sufficient funds) you must cancel and re-submit the case.
To edit a recorded trial payment, click on the Record Trial Payments icon then select the "Edit" link next to the payment you would like to amend. You may only make changes to the "Actual Payment Date" and "Actual Payment Amount" fields.
Interactive training for these functionalities is also available in the SMDU UI Learning Series.