FIT on your paycheck is federal income tax withheld: the amount your employer took out of this paycheck and sent to the IRS toward your income tax for the year. On a pay stub the same line can read FIT, FITW, FIT WH or FWT.
FIT taxable wages (or Fed taxable gross) is the wage figure that the FIT amount was calculated on. It is not the same as gross pay.
In brief. FIT is the federal withholding line. FIT taxable wages is the base it was computed on, gross pay minus pre-tax deductions. Both move when you file a new Form W-4.
FIT, FITW, FIT WH, FWT: what the codes on a pay stub mean
Payroll systems abbreviate the federal income tax line in different ways. The IRS Tax Withholding Estimator FAQs list FIT, FITW, FITC, Fed W/H and Fed tax as names for it. These all mean the same thing:
| Code on the stub | Stands for | Same as FIT? |
|---|---|---|
| FIT | Federal income tax | Yes |
| FITW | Federal income tax withholding | Yes |
| FIT WH, FIT W/H | Federal income tax withheld | Yes |
| FWT, FWH, Fed W/H | Federal withholding tax, federal withholding | Yes |
| Fed Tax, Fed Inc Tax, FED IT | Federal income tax | Yes |
| SIT, SWT | State income tax withheld | No, the state version |
| OASDI, SS, FICA-SS | Social Security tax | No, see OASDI on a paycheck |
| MED, FICA-MED | Medicare tax | No |
FIT taxable wages, sometimes printed as Fed taxable gross, is a wage figure, not a tax. It is the amount the FIT line was worked out on.
What are FIT taxable wages?
Start with gross pay for the period and subtract the deductions that federal tax law treats as pre-tax:
- Traditional 401(k), 403(b), 457(b) and similar retirement deferrals
- Health, dental and vision premiums paid through a Section 125 plan
- Health savings account and flexible spending account contributions
- Some commuter and dependent care benefits
Not all of these lower Social Security and Medicare as well; pre-tax deductions sorts them by which taxes each one reduces, with the 2026 limits.
What is left is FIT taxable wages. A 2,500.00 gross paycheck with a 150.00 401(k) deferral and a 95.00 health premium has FIT taxable wages of 2,255.00.
Note that retirement deferrals reduce FIT taxable wages but not Social Security and Medicare wages. Section 125 items reduce both. That is why a stub can show three different wage bases.
In the example above, Social Security and Medicare wages are 2,405.00 because only the health premium comes off. The stub carries 2,500.00, 2,405.00 and 2,255.00 side by side.
How is the FIT amount calculated?
Employers use the tables in IRS Publication 15-T. For a Form W-4 from 2020 or later, the automated method works like this:
- Annualize the period's FIT taxable wages (multiply by the number of pay periods in the year).
- Adjust for the W-4: add Step 4(a) other income, then subtract Step 4(b) deductions and the standard amount on Worksheet 1A. The standard amount is skipped when the Step 2 box is checked.
- Look up the annual tax in the table for the filing status (single, married filing jointly, or head of household), using the higher Step 2 table if that box is checked.
- Subtract Step 3 credits (dependents).
- Divide by the number of pay periods and add any Step 4(c) extra withholding.
Run the example through those steps for a single filer with a 2020 or later W-4 and no adjustments, and the FIT line on that biweekly paycheck is 186.75 under the 2026 tables. Social Security is 149.11 and Medicare 34.87 on the 2,405.00 base.
Here is that stub line by line, computed by our generator. The three wage figures sit in step 5, and FIT is step 6.
| Step | Line | Amount |
|---|---|---|
| 3 | Regular pay (80 hours at $31.25) | $2,500.00 |
| 4 | Gross pay | $2,500.00 |
| 5 | 401(k) deferral, 6% of gross | -$150.00 |
| 5 | Health premium (Section 125) | -$95.00 |
| 5 | Income tax wages (gross minus both) | $2,255.00 |
| 5 | Social Security and Medicare wages (gross minus health only) | $2,405.00 |
| 6 | Federal income tax | -$186.75 |
| 7 | Social Security | -$149.11 |
| 7 | Medicare | -$34.87 |
| 8 | Georgia income tax | -$83.74 |
| 9 | After-tax deductions (none in this example) | $0.00 |
| 10 | Net pay (gross minus taxes and deductions) | $1,800.53 |
Our pay stub generator performs exactly these steps for the 2026 tax year and shows the result on the FIT line. The methodology page lists the source tables.
How does FIT differ from Social Security and Medicare?
| Line | What it is | How it is set |
|---|---|---|
| FIT | Federal income tax withholding | Tables plus your W-4 |
| Social Security (OASDI) | Retirement and disability insurance | 6.20% of wages up to the SSA wage base of $184,500 |
| Medicare (HI) | Hospital insurance | 1.45% of all wages |
FIT is an estimate of the year's tax spread across paychecks. Social Security and Medicare are the final tax. The tax return does not settle them up, except for a credit when two or more employers together withheld too much Social Security.
SIT, state income tax, is the state version of FIT: withheld from the same paycheck under the state’s own tables and settled on the state return. Stubs from states that do not tax wages have no SIT line.
Why does FIT look too high or too low?
FIT changes with wages, so a paycheck with overtime or a bonus withholds more; how bonuses are withheld shows both methods on one example. It also changes when you file a new W-4.
If the year-to-date FIT figure looks far from what you expect to owe, the IRS Tax Withholding Estimator can suggest W-4 changes. Two-income households often under-withhold unless the Step 2 box is checked on both W-4s; how to fill out a W-4 shows the gap for one couple.
