In order to correct a customer’s balance we will go to:

Customers --> Customers

From here we will see the list of all our clients.

We will click on the button to edit the client we want.

When we open a new window we will go to "Billing and Collection" in the menu on the left and then to "Balance" as shown in the image provided.

Click on "Balance Correction" and the following window will open:

We will then enter the amount that we want to correct and accept.