When a client disengagement letter is issued, an automation is created to stop repeating invoices being raised and sent to Xero (or other accounting software) and the client is marked as 'No Longer a Client' in eg. Accountancy Manager (or equivalent). Likewise if this could be a two way street, so if the client is marked as NLAC in AM and the data is then fed back into GP to stop the monthly invoice being raised.
Totally agree that this would be useful....although in our case we use Pixie as our Practice Management Software