If you've sent an invoice to QuickBooks Online with incorrect information, you'll want to bring it back to LeanLaw before editing out the mistakes.
Once your invoices have been created, and are view-able in the Open of the Billing tab, open the invoice. At the bottom of the invoice is the Back to Draft button. Click that to return the invoice from QuickBooks to LeanLaw.
To Undo a Draft invoice, check here.