In a fee table, you can set any row as Optional. This allows your client to select if they want to opt in for this fee.
To set a fee as optional, you can click in the table and hover over the row. You'll see several icon appear to the right of the fee. Click the gear icon to edit an existing row, or the + button to add a new row.
From there, check on "Optional for clients"
This will add a check box to that row.
As soon as the your client clicks the check box, it will be included in the total.
See also: Fee Types