How to create pretax parking payroll element that's pre-tax for Federal, Social Security & Medicare

We created a payroll element as a pretax deduction for parking in our development environment, and it should be pre-tax for Federal Income Tax (FIT), Social Security and Medicare. But it's only behaving as pretax for FIT. We did not select a Secondary Classification because the options didn't appear to be applicable. How do we create a payroll element as a pretax deduction for parking that's pre-tax for Federal, Social Security & Medicare?