You can cancel the custom On-Demand Scan and policy based On-Demand Scan running on the client system from ePO - On-prem.
Select Menu → Client Tasks → Client Task Catalog.
From Client Task Types, select Endpoint Security Threat Prevention → Cancel On-Demad Scan.
Click New Task.
Make sure Cancel On-Demad Scan is selected and click OK.
Provide the task name and click Save.
Click Menu → System Tree → Systems and select the client system.
Click Actions → Agent → Run Client Task Now.
In the Run Client Task Now page, do the following:
In the Product list, select Endpoint Security Threat Prevention.
In the Task Type, select Cancel On-Demand Scan.
In the Task Name, select the required task name.
Click Run Task Now.
Click Server Task Log to check the status of the cancelled scan.
The ongoing scans are cancelled and you can reinitiate the scans if required.
Note
You cannot cancel the Full Scan or Quick Scan initiated from the Trellix ENS Client.