To reverse an AR invoice once it has been posted, simply select the invoice through the Sales|AR Invoice screen, right click and select "Reverse" or open the invoice and click on the reverse button.  This will create a reversal invoice for the opposite amount and same date as the original.  To print a Credit Memo if necessary, simply print that negative invoice.  You will need to post the reversal invoice to return the inventory to stock, un-post the shipment (if it was created through a sales order) and generate the JV entry.

If you wish to create a partial credit or credit the customer on a different date, enter a NEW negative qty invoice through the Sales| AR Invoice screen for the amount you wish to credit. If an invoice amount is negative, Pilot will automatically change the AR Invoice to a "Credit Note" for printing and emailing.

Both the original and credit invoice will be available in AR Payments to record the customer payment.