Correct or Cancel Offline CC Transaction

If you are not able to void a payment in Billing -> Invoices -> Void Payments enter an invoice for the negative amount and apply the invoices to each other by entering 0.00 for the payment amount and then selecting both the positive and the negative invoice amounts. When entering a new invoice, you can select the date right from the first screen. This gives you the option of changing the date to a previous day.