By default, the SLA timer will be paused when the ticket is in pending status. While working on a ticket you may need to await further details from the end-user or a supplier. This is also the case if the ticket is waiting for a reply from a vendor, developer, or service provider. In these cases, you can pause the SLA timer by selecting a status such as "awaiting customer reply" or “awaiting 3rd party response”. The SLA time can be toggled on/off for such status in the settings via Edit Ticket status.
You can also create new ticket statuses according to your requirements and configure your SLA timer to be toggled on/off in Settings/Ticket Status/Create Ticket Status