> ## Documentation Index > Fetch the complete documentation index at: https://docs-test.symmetry.com/llms.txt > Use this file to discover all available pages before exploring further. # U.S. Federal Taxes Overview > Overview of the U.S. federal taxes calculated by the Symmetry Tax Engine, including FIT, FICA, FUTA, railroad taxes, and pension withholding. The Symmetry Tax Engine (STE) calculates the core U.S. federal payroll taxes for each pay period, covering employee income tax withholding, the Social Security and Medicare programs, federal unemployment, railroad-specific taxes, and withholding on pension and annuity payments. This page introduces each federal tax category. The detailed setup instructions, miscellaneous parameters, and example calculations live on the dedicated pages linked below. ## What the STE covers * **Federal Income Tax (FIT)** — withheld from employee wages based on the employee's Form W-4. The STE supports both the pre-2020 W-4 (using allowances) and the 2020-and-later W-4, calculated per IRS Publication 15-T. FIT is identified by tax ID `00-000-0000-FIT-000`. * **FICA (Social Security and Medicare)** — the Social Security tax (`FICA`/`ER_FICA`, 6.2% each for employee and employer) and the Medicare tax (`MEDI`, `MEDI2`, `ER_MEDI`, 1.45% plus the 0.9% Additional Medicare tax on wages over \$200,000). * **Federal Unemployment Tax Act (FUTA)** — an employer-only tax (`ER_FUTA`) calculated on FUTA gross wages. The STE always requires the FUTA rate to be set so you can control credit reductions and other rate adjustments. * **Railroad Taxes (RRTA and RUIA)** — federal taxes for eligible railroad workers. RRTA (Tier I and Tier II) is calculated instead of FICA, and RUIA is calculated instead of FUTA. * **Pension & Annuity Payments (W-4P/W-4R)** — withholding on periodic (Form W-4P) and nonperiodic (Form W-4R) pension and annuity payments, which reuse the FIT withholding tables and the `00-000-0000-FIT-000` tax ID. ## Federal tax pages Employee income tax withholding based on the Form W-4, for both pre-2020 and 2020-and-later forms. Social Security and Medicare taxes, including the Additional Medicare tax and employer contributions. Employer-only unemployment tax calculated on FUTA gross wages, with a required rate. Tier I and Tier II RRTA and railroad unemployment (RUIA) taxes for eligible railroad workers. Withholding on periodic and nonperiodic pension and annuity payments. When gross wages at the federal level (`00-000-0000`) are not explicitly specified, the STE will use the sum of the local locations' wages as the federal gross wages, preserving each wage type. See [Federal Income Tax (FIT)](/ste/taxes/federal/federal-income-tax-fit) for details on wage defaulting.