Locate the invoice that you want to void and click its ID.
The invoice details will appear below the record of the invoice you are viewing. The other option is to click on the magnifying glass icon in the Available Operations column to view the invoice details.
Click Create an Invoice Reversal in the Tools section of the page.
Click Yes, create a credit note and void this invoice.
Go to Finances > Invoices again. You will see two entries for each invoice.