Select the Account Payment tab.  Find the invoice that you want to write off as a Bad Debt in the Invoice list (tick Show All if it is not visible). Click on [+] to drill down to the item details. If the invoice contains more than one item, they will appear as a list. Highlight each item and click on Bad debt in the action list

A corresponding Bad Debt and Bad debted items will exist. A note will be added to the patient's alerts.