Form W-4 Explained: How Your Withholding Is Set
Quick answer
Form W-4 tells your employer how to estimate your federal income tax, but each employer sees only its own paycheck. A married couple earning $60,000 each owes $10,040 on 2026 figures, yet two employers withholding from a plain W-4 take only $2,840 each, or $5,680 in total, leaving $4,360 to pay at filing. Step 2 of the form closes the gap: checking the box on both W-4s withholds exactly $10,040 when the two salaries are equal, and the Multiple Jobs Worksheet adds $4,760 a year to one job, slightly more than needed.
Form W-4 is the only instruction your employer has about your federal income tax. It does not report your tax bill; it sets the estimate that comes out of each paycheck, and the annual return then trues that estimate up.
Since 2020 the form has had no allowances. Instead it asks for your filing status, whether there is another job in the household, the credits you expect, and any income or deductions the employer cannot see. This guide follows those answers through the IRS's own withholding tables for 2026 to show what each one actually does to a paycheck, and where the form is exact and where it is not.
What your employer does with the form
Payroll software follows IRS Publication 15-T. It annualises the pay for the period, adds any other income you entered in Step 4(a), subtracts any deductions from Step 4(b), and then subtracts a further fixed amount: $12,900 for married filing jointly, or $8,600 otherwise. The result is run through an annual rate table, the credits from Step 3 are taken off, and the answer is divided back across the year's pay periods. Any extra amount from Step 4(c) is added to each paycheck on top.
The fixed amount is half of how the standard deduction gets in. The other half is a 0% band at the bottom of the table: the first $19,300 for joint filers and $7,500 for single filers. $12,900 plus $19,300 is $32,200, and $8,600 plus $7,500 is $16,100, which are exactly the 2026 standard deductions. So a plain W-4 assumes the standard deduction, applied in full, to this one job.
An employer has no way to know about a second job or a working spouse. Unless Step 2 is completed, every payroll in the household gives its own salary the full standard deduction and the full low-rate brackets, as though it were the household's only income.
Why two earners come up short
Take a married couple filing jointly, each earning $60,000, with no other income, no pre-tax deductions and no credits. On 2026 figures their $120,000 of combined wages, less the $32,200 standard deduction, leaves $87,800 of taxable income and $10,040 of federal income tax.
Each employer, given a plain W-4 marked married filing jointly, subtracts $12,900 from $60,000 and looks up $47,100 in the table: $2,840 a year. Two employers withhold $5,680 between them. The household is short by $4,360 (about $168 for each of the 26 biweekly paychecks) and finds out at filing time.
Nothing was miscalculated. Each payroll applied the standard deduction and the 10% and 12% bands to its own salary, so the household received both twice. The same thing happens to one person with two jobs, which is why Step 2 is phrased as "multiple jobs or spouse works".
Three ways to complete Step 2, and what each withholds
Step 2 offers the IRS online estimator, a worksheet, or a checkbox. The estimator is the most accurate and is the only option the form recommends when there is self-employment income. The other two can be worked out from the tables, and they behave differently depending on how evenly the household's pay is split.
- The checkbox halves the standard deduction and the brackets for each job. With equal salaries that is exactly right: $5,020 from each job, $10,040 in total. With unequal salaries it over-withholds, here by $2,350, because the higher-paid job is pushed into the 22% band on income that, for the household as a whole, sits in the 12% band. The form itself warns that the excess grows with the gap in pay.
- The worksheet looks up a single extra amount from a table ($4,760 for two jobs in the $60,000–$69,999 range) and adds it to the higher-paying job through Step 4(c), at $183.08 per biweekly paycheck. It lands a little high in both cases, by $400 and $640, which errs toward a small refund rather than a bill.
- Leaving Step 2 blank is the only option that falls short, and it does so in both cases.
| Annual figures, 2026 | $60,000 + $60,000 | $90,000 + $30,000 |
|---|---|---|
| Federal income tax owed | $10,040 | $10,040 |
| Withheld with Step 2 left blank | $5,680 | $6,440 |
| Withheld with the Step 2(c) box checked on both | $10,040 | $12,390 |
| Withheld using the Multiple Jobs Worksheet | $10,440 | $10,680 |
Married filing jointly, wages only, standard deduction, no credits. Withholding computed with the 2026 Publication 15-T annual percentage method; the worksheet amount is read from the 2026 Form W-4 table.
Steps 3 and 4: credits, other income and extra withholding
Step 3 lowers withholding by the credits you expect. The 2026 form uses $2,200 for each qualifying child under 17 and $500 for each other dependent, for households with income of $200,000 or less ($400,000 married filing jointly). The credit comes off the annual withholding figure, so one child reduces it by $2,200, about $84.62 per biweekly paycheck.
Step 4(a) adds income that has no withholding of its own, such as interest, dividends or retirement income, so that the tax on it is collected through the paycheck instead of through estimated payments. Step 4(b) does the opposite for deductions beyond the standard deduction; on the 2026 form that includes itemized deductions and the newer deductions for qualified tips, overtime, passenger-vehicle loan interest and seniors. Step 4(c) is a flat extra amount per paycheck, and it is where the Multiple Jobs Worksheet result goes.
- In a household with more than one job, complete Steps 3 through 4(b) on one W-4 only, ideally the one for the highest-paying job. Entering the same child credit on both spouses' forms takes it off twice.
- Steps 3 and 4(b) both raise take-home pay now and shrink the refund later. Overstating them moves the bill to April rather than removing it.
- Step 4(c) is the simplest correction mid-year: divide the expected shortfall by the paychecks left in the year.
When to file a new one
A W-4 stays in force until you replace it, so the one filed at the start of a job can be years out of date. The form suggests rechecking whenever marital status, the number of jobs in the household, dependents, other income, deductions or credits change, and at the start of each year.
Claiming exemption from withholding is the exception: it lasts one calendar year. Someone who claims exempt for 2026 must file a new W-4 by February 16, 2027, and is only eligible if they had no federal income tax liability in 2025 and expect none in 2026.
To see whether the current setup is on track, estimate the year's tax with the Federal Tax Refund Calculator and compare it with the federal income tax withheld year to date on your latest pay stub, scaled to a full year. The Paycheck Calculator shows what a change will do to each check.
Frequently Asked Questions
Do W-4 allowances still exist?
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Not on the current form, which dropped them in 2020. An employee who has not filed a new W-4 since 2019 can stay on the old one, and payroll still honours it: Publication 15-T for 2026 values each old allowance at $4,300 of annual wages.
Should both spouses check the Step 2 box?
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If you use the checkbox, yes. It only works when it's ticked on the W-4 for both jobs. It is accurate when the two salaries are similar. When one earns much more than the other it withholds too much, and the Multiple Jobs Worksheet or the IRS estimator is the closer option.
Does the W-4 change Social Security and Medicare?
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No. The W-4 sets federal income tax withholding only. Social Security and Medicare are flat percentages of wages that every employer withholds regardless of what the form says.
Why did my withholding go up after I married?
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Usually it went down, because the married-filing-jointly table has a wider 0% band and wider brackets. If both spouses work and neither completes Step 2, that lower withholding is applied by both employers, which is the most common route to an unexpected bill in the first year of marriage.
Sources
- IRS Form W-4 (2026) — Employee's Withholding Certificate — The form and its instructions. Backs the description of each step: the three Step 2 options and the warning that the checkbox over-withholds as the gap in pay grows; the $2,200 and $500 Step 3 amounts and their $200,000/$400,000 income condition; the 2026 Step 4(b) deductions including tips, overtime, vehicle loan interest and seniors; completing Steps 3–4(b) on one form only; the exemption conditions and the February 16, 2027 deadline; and the Multiple Jobs table that gives $4,760 and $4,240 for the two examples.
- IRS Publication 15-T (2026) — Federal Income Tax Withholding Methods — The employer's method. Worksheet 1A gives the $12,900 and $8,600 subtractions and the $4,300 value of a pre-2020 allowance; the 2026 annual percentage method tables, standard and Step 2 checkbox, give every withholding figure in the comparison table.
- IRS Revenue Procedure 2025-32 — inflation adjustments for 2026 — The 2026 standard deductions ($32,200 joint, $16,100 single) and the married-filing-jointly rate table used to compute the $10,040 owed in both examples.