How to Figure the Taxable Income With an FSA Account

1). Verify that your FSA contributions come out of your paycheck on a pretax basis. You can find this information in the documents you received when you opened the FSA or you can ask your human resources representative.
2). Find the total year-to-date FSA contributions listed on your most recent pay stub. Add that amount to any other pretax contributions you make. Examples include contributions to a 401k or 403b retirement plan, and your medical and dental insurance.
3). Subtract the total of your pretax contributions, including contributions to your FSA, 401k and health insurance, from the gross wages listed on your pay stub. The result is your taxable income, after all pretax contributions have been factored in.