At present laboratory orders are submitted the moment an invoice is saved.
This can be through OK or Apply, or via auto-save.
Once a laboratory order is submitted, tests cannot be added or removed. To change a order requires cancelling the existing one and submitting a new one, which can only be done by removing the existing charge(s) and entering a new one that generates the desired test(s).
To limit the need to cancel investigations, defer all laboratory order submission till OK/Apply is pressed.