1. If the invoice is posted and paid, void the associated check.
    Note: If the check is marked as Reconciled it cannot be voided, and the invoice cannot be deleted.
  2. In Records, Invoices, open the invoice.
  3. Select File, Delete from menu bar.

Note:  As long as the Invoice was posted before it was deleted, a record of it will be kept with the vendor record.  You will be able to see it based on your user settings.  If the Invoice was not posted before it was deleted, there will be no record of it.