An unusual way to exclude terminated volunteers in the Volunteer Reporter v5.7 uses the choice "Is Blank" on the Termination Cause filter limitation. This method perhaps makes you tune up your database a bit. In order for this to work, first make sure every terminated volunteer in the inactive Volunteers records has a cause of termination. An easy way to check those records is to open Volunteers | Inactive | Dates tab. Use the down arrow on the keyboard to cycle through the inactive records to verity that every volunteer record has a value in the Termination Cause field. If one is blank, edit it and select a cause. [Below is also a review of how to terminate a volunteer.]
Filters | Add Filter | name it: Exclude Term. Vols. | Save.
In the Volunteer Limits tab, scroll way down to find and select Termination Cause. Click the Edit Limitation button.
Instead of the typical selection of a cause of termination, put the dot next to 'Is blank' and save the setting. Do not select/set any double chevrons in the list.
Save the setting. Close filters.
Now you can use this exclude-terminated-volunteers filter on any hours or statistics report to exclude terminated volunteers. You never need this filter for most reports because by default most reports already exclude terminated volunteers. Active volunteers' cause of termination field is always blank, making the filter redundant.
The Hours and Statistics reports are the big exceptions which do include terminated volunteers if they served hours during the time defined for the report. What makes this filter work to exclude terminated volunteers is the Reporter's hidden filter for hours reports which includes terminated volunteers. By adding the blank field as a filter limitation, you make the Reporter look for  inactive volunteers plus  without a cause of termination. It searches within the inactive volunteers records but within those it cannot satisfy both conditions since every terminated volunteer in your database defines a cause of termination [e.g., the field is not blank]. Fortunately, you don't have to follow the logic to use the filter.
The following steps detail terminating a volunteer, editing a volunteer's cause of termination, and adding a cause of termination to the reference codes.
If a terminated volunteer's Termination Cause is blank, click the Edit button and select a cause. OK.
To terminate a volunteer, open Volunteers | find the volunteer | Dates & Info tab | Edit | click the Terminate button | OK. Be sure to give the volunteer a Termination Cause, perhaps "temporary" or "health problems." Be consistent so that you can filter on that value for mailing labels or other inquiries.
Select a Cause of Termination. Then click OK.
When you click OK to confirm terminating the volunteer, a message usually says, "Do you want to terminate this volunteer and all of the placements for this volunteer?" You must click "Yes" or else not terminate the volunteer.
If you need to add categories to the Termination Cause, click on Reference Codes | Causes-of-Termination Add | and type a new category.
Any changes to the Reference Codes will not display on the Volunteer screen until you close and reopen Volunteers to refresh the data.
To add a new category in the middle of a termination procedure, you would have to cancel the procedure and go change the Causes-of-Termination values. Alternatively, you could change the Causes-of-Termination value after terminating the volunteer and then edit the volunteer's record in the Inactive section.