If you have an invoice already in the QuickBooks billing folder in LeanLaw and you need to change the date prior to sending it to your client, you can do so without having to bring the invoice back to the draft stage.
Click the triple dots at the end of the invoice and choose “Open in QuickBooks". This will open the invoice in its original form in your QuickBooks account.
Change the date while you are in that invoice in QuickBooks.
Click the dark "Save" button (do not click the green "Save and Send" button).
Go back to LeanLaw and refresh your screen. The new invoice date will now appear and you can deliver to your client via their normal delivery method.