Within Natural HR you have the ability to condition the start of an offboarding workflow on a particular exit reason. 

For information on creating an exit reason please view the article here

To link to an exit reason to a workflow:

Administration > HR > Data Management > Exit Reasons

Select to edit a current exit reason

Go to the workflow field and enter your mouse cursor into the field. This will provide you with a drop-down of available workflows you can use to link to this exit reason.

Once you make an employee a leaver and select the relevant reason it will then automatically trigger the offboarding workflow.

A workflow can be attached to more than one exit reason and different workflows can be used for different exit reasons.

I.e. you may have an offboarding workflow for your voluntary reasons and then a separate workflow for all your involuntary reasons.

Please note if you have any restrictions on your workflow to not include particular categories then if the employee falls within this category even if the exit reason is selected it will not work for this employee.