What Is FIT Tax? Federal Income Tax Withholding on Your Paycheck, Explained (2026)

What is FIT tax on a paycheck: it is federal income tax withheld from wages as a prepayment toward the annual bill, not a separate tax.

FIT tax is the federal income tax withholding line on a pay stub. An employer estimates the year’s federal income tax from the employee’s Form W-4 and the IRS Publication 15-T tables, withholds a share from each paycheck, and reports the total in Box 2 of Form W-2. It is a prepayment settled on Form 1040, not an extra tax.

By Craig Wear, CFP® | Last reviewed: October 14, 2026

This guide decodes the FIT line, rebuilds it from the 2026 IRS tables, and follows it into retirement, where the same withholding rules can help cover the tax on a Roth conversion.

What does FIT mean on a pay stub?

FIT on a pay stub means federal income tax withheld from that paycheck and sent to the IRS on the employee’s behalf. FIT, FWT, Fed Tax, and Federal Withholding are all labels for the same deduction.

Unlike Social Security and Medicare, which are flat and generally final when withheld, FIT is an estimate compared with the actual tax on the annual return. The payroll taxes guide covers the FICA side in depth, so the table below focuses on reading the stub.

Source: IRS Publication 15 (2026).

How does an employer calculate FIT?

An employer calculates FIT by annualizing the employee’s taxable pay, adjusting it for the Form W-4 entries, and running it through the IRS Annual Percentage Method table in Publication 15-T. Automated payroll systems use this percentage method; manual payroll can use wage bracket tables that produce very similar results.

An employee who completes only Steps 1 and 5 of the 2026 Form W-4 is withheld on filing status, pay, and pay frequency alone. The sequence below follows Worksheet 1A, the employer’s worksheet for automated payroll.

1. Start with gross pay. Salary, hourly wages, commissions, and tips for the pay period.
2. Subtract pre-tax deductions. Traditional 401(k) deferrals and cafeteria plan health premiums come out first, leaving FIT taxable wages.
3. Annualize. Multiply by the number of pay periods (26 for biweekly, 52 for weekly, 12 for monthly).
4. Apply the Form W-4 adjustments. Add Step 4(a) other income, then subtract Step 4(b) deductions and, unless the Step 2 box is checked, $8,600 (single or head of household) or $12,900 (married filing jointly).
5. Look up the annual table. Find the row in the Publication 15-T Annual Percentage Method table, then take the base amount plus the marginal percentage of the excess over the row floor.
6. Convert back to one paycheck. Divide by the pay periods and subtract the per-period share of Step 3 credits (zero is the floor).
7. Add any extra withholding. The Step 4(c) dollar amount is added on top, and the result is the FIT line on the pay stub.

With no Form W-4 on file, Publication 15 tells the employer to withhold as if the employee checked Single or Married filing separately with no other entries.

Worked example: FIT on a $65,000 salary in 2026

A single filer earning $65,000 who defers 6% to a traditional 401(k) would have about $198.15 of FIT withheld from each biweekly paycheck under the 2026 tables. The example below is hypothetical and assumes a 2026 Form W-4 with only Step 1 (single) completed and no other pre-tax deductions.

Now compare that with the actual 2026 tax. Box 1 wages of $61,100 minus the $16,100 standard deduction leave $45,000 of taxable income. Under the 2026 brackets announced by the IRS, that is 10% of the first $12,400 ($1,240) plus 12% of the remaining $32,600 ($3,912), or $5,152. The year’s withholding ($198.15 times 26, or $5,151.90) lands within about ten cents of the bill.

That match is by design: for one job and the standard deduction, withholding tracks the real liability, and refunds or balances due come from what the W-4 does not know, such as a second job or investment income. The tax on a $40,000 salary walks through the same bracket math at a lower income.

Why do the 2026 withholding tables mirror the tax brackets?

The 2026 withholding tables mirror the tax brackets because each table threshold equals a 2026 bracket threshold plus the portion of the standard deduction that sits inside the table. For a single filer, the $7,500 zero band plus the $8,600 worksheet subtraction equals the $16,100 standard deduction, so every row is shifted by exactly $7,500 after that subtraction.

The married filing jointly table works the same way: a $19,300 zero band plus the $12,900 subtraction equals the $32,200 joint standard deduction, and the 24% row ends at $422,850, which is the $403,550 top of the joint 24% bracket plus $19,300. Checking the Step 2 box switches to a schedule with half the zero band ($8,050 single, $16,100 joint) and no subtraction, splitting the standard deduction across two jobs.

Why is FIT $0 or different on some paychecks?

FIT is $0 when annualized taxable wages fall inside the built-in standard deduction, and it changes when pay, pre-tax deductions, or W-4 entries change. With a plain W-4, no FIT is withheld until FIT taxable wages pass $16,100 a year for a single filer (about $619 biweekly) or $32,200 for married filing jointly (about $1,238 biweekly).

Other common reasons the line moves or disappears:

• Hours vary. Each check is annualized on its own, so a short week can fall below the zero band.
• Pre-tax deductions change. A higher traditional 401(k) deferral lowers FIT taxable wages at once.
• Exempt status. An employee who certifies both conditions (no federal income tax liability in 2025 and none expected in 2026) has no FIT withheld, and the 2026 form says a new certificate is due by February 16, 2027.
• W-4 credits and deductions. Step 3 lists $2,200 per qualifying child under 17 and $500 per other dependent; large Step 3 or 4(b) entries can push FIT to zero.
• A bonus in the check. Supplemental pay follows separate rules, covered below.

How does FIT connect to a refund or a balance due?

FIT connects to the refund or balance due because the year’s total withholding, shown in W-2 Box 2, is subtracted from the tax calculated on Form 1040. If withholding exceeds the tax, the difference is refunded; if it falls short, the difference is owed with the return. When that balance due grows, see why taxes are higher this year.

A shortfall can also trigger an underpayment penalty. The penalty generally does not apply when the tax owed after withholding is under $1,000 (Instructions for Form 2210), or when withholding and estimated payments cover the smaller of 90% of the 2026 tax or 100% of the 2025 tax, rising to 110% if 2025 AGI exceeded $150,000 ($75,000 married filing separately), per IRS Publication 505 for 2026.

Timing is where withholding differs from estimated payments. The Instructions for Form 2210 treat withheld federal income tax as paid in four equal parts on the installment due dates unless the taxpayer shows otherwise, so extra withholding late in the year can count as if it had been paid evenly. Quarterly estimated tax payments, by contrast, are credited on the date paid. The same rules apply to retirees’ pension and IRA withholding.

How can FIT withholding be changed?

FIT withholding is changed by giving the employer a new Form W-4, which must take effect no later than the start of the first payroll period ending on or after the 30th day after the employer receives it (IRS Publication 15). The IRS recommends its Tax Withholding Estimator for anyone starting mid-year, holding two jobs, or expecting other income.

The 2026 Deductions Worksheet is new: it lets eligible workers reflect One Big Beautiful Bill Act deductions in each paycheck instead of waiting for a refund, subject to the income limits printed on the worksheet (IRS Form W-4, 2026). Workers over 65 who are still earning a paycheck can see the senior deduction reflected in their FIT this way. The OBBBA retirement tax changes page covers the wider law.

How is FIT withheld on a bonus?

FIT on a bonus is usually withheld either at a flat 22% or by adding the bonus to regular wages and running the combined amount through the tables; supplemental wages above $1 million in a year must be withheld at 37% regardless of the W-4 (IRS Publication 15). The flat 22% option is available only if income tax was withheld from the employee’s regular wages in the current or prior year.

A common misconception is that bonuses are taxed at 22%. They are withheld at 22%; the tax is figured on the annual return at the employee’s actual marginal tax rate. In the hypothetical $65,000 example above, a separate $3,000 bonus withheld at 22% would have $660 of FIT taken out, yet the bonus would raise taxable income from $45,000 to $48,000, still inside the 12% bracket, so the tax on it would be about $360 and the remaining $300 would generally come back at filing, all else equal. For a high earner in the 32% or 35% bracket, the same 22% flat rate can under-withhold. The same withholding logic applies to lump sums of past wages, explained in whether back pay is taxed at a higher rate.

Publication 15’s own example shows the gap: on a $1,000 bonus to a single employee paid $2,000 a month, the aggregate method withheld $114 and the flat-rate method $220. Social Security and Medicare apply either way.

Does FIT still apply in retirement?

FIT still applies in retirement, but each income source uses its own form instead of the W-4. Periodic pensions and annuities use Form W-4P, IRA and other nonperiodic distributions default to 10% withholding on Form W-4R (an employer plan’s eligible rollover distribution paid to the owner carries a mandatory 20%), and Social Security uses Form W-4V with flat 7%, 10%, 12%, or 22% choices. The full source-by-source rules sit in the tax withholding in retirement guide.

Withholding also matters for Roth conversions, which add taxable income with no paycheck behind it. A working spouse can add a Step 4(c) amount on a W-4, which counts as paid evenly through the year, or tax can be withheld from the IRA itself, with the trade-off that withheld dollars are not converted. The guide on using IRA withholding to pay Roth conversion tax covers that trade-off, and a financial professional can model how much tax a conversion may add before any withholding change.

Frequently asked questions

This article is for educational purposes only and is not individualized investment, tax, or legal advice. Consult a qualified professional about your specific situation.