On your final invoice in QuickBooks Online, your firm may need custom fields like Matter Name and ID. Let's get those added.
First steps are to select your Matter Name and Client and Matter ID fields in Invoice Settings.
Once your LeanLaw settings are completed, jump it your QuickBooks Custom Form Settings, and select Header.
In Custom, both of your custom fields, and save the form. These will now appear on your invoices, below the address information.