Important: It's good business practice to keep a complete record of all transactions, including invoice numbers. Because you can still access voided, but not deleted, invoices, most of the time you should void invoices instead of deleting them. Once you void or delete an invoice, the change is permanent. If you void or delete an invoice and want to restore it later, you'll have to create a new invoice.
To do this task
Open the invoice you want to void.
Choose Customers > Customer Center.
If you know the customer's name:
From the Customers & Jobs list, select the customer.
In the transactions pane to the right, click the Show drop-down arrow and select Invoice.
If you don't know the customer's name:
Click the Transactions tab.
From the transaction types list, select Invoices.
(Optional) Use the Filter By and Date drop-down arrows to narrow the results.
Double-click the invoice to open it.
From the main QuickBooks menu, choose Edit > Void Invoice.
Save the change.
The invoice amounts are changed to zeros, and the invoice is stamped as VOID.
Delete an invoice only if you haven't printed or saved it.
Open the invoice you want to delete.
From the main QuickBooks menu, choose Edit > Delete Invoice.
Click OK to confirm the deletion.