How should I set up my W-4 for 2025?

What the W-4 actually does

Your W-4 tells your employer how much federal income tax to withhold from each paycheck. The IRS redesigned the form in 2020 — no more "allowances." Instead, you enter dollar amounts directly: your dependents (as credits), your other income, your itemized deductions (if any), and any extra you want held back per paycheck.

If you under-withhold, you owe in April plus possible underpayment penalties. If you over-withhold, you get a refund — which is just the IRS giving back your own money interest-free. Getting the W-4 right means landing close to zero in either direction.

How to fill out the W-4, step by step

Step 1: Name, address, SSN, filing status. The status determines which tax brackets and standard deduction apply.

Step 2: Multiple jobs — for couples where both work, or single people with two jobs. Three options:

• 2(a) — Use the IRS online estimator (slowest, most accurate).
• 2(b) — Use the worksheet on page 3 (math-heavy, accurate for asymmetric incomes).
• 2(c) — Just check the box. Works when both jobs pay roughly similar amounts.

Step 3: Dependents. Multiply children under 17 by $2,200 (post-OBBBA) and other dependents (parents, older kids) by $500. Enter the total as a dollar amount, which directly reduces your withholding.

Step 4(a): Other income that won't be on a W-2 — side hustle profit, dividends, interest, retirement distributions.

Step 4(b): Deductions above the standard deduction. Only fill in if you're itemizing.

Step 4(c): Extra withholding per paycheck. ON TOP of normal withholding.

Step 5: Sign and date. Hand to HR.

Finding your pre-tax payroll deductions

The W-4 doesn't ask about pre-tax contributions directly, but they change how much federal income tax your employer should withhold. Our calculator handles this for you, but the number has to come from your pay stub. Here's how to find it.

What counts as pre-tax (enter this in the field):

• Traditional 401(k), 403(b), 457(b) — the workhorse retirement deferrals. Look for "401(k)", "Pre-Tax 401k", "Trad 401k", or your plan's vendor name (Fidelity, Vanguard, etc.) on your pay stub.
• Health Savings Account (HSA) contributions made through payroll — labeled "HSA", "Health Savings", or similar.
• Flexible Spending Account (FSA) — both health FSA and dependent-care FSA. Labeled "FSA", "Healthcare FSA", "Dependent Care".
• Traditional IRA via payroll deduction (rare but exists in some plans).
• Commuter benefits (transit / parking) — typically up to $325/month each in 2025.

What does NOT count (leave it out):

• Roth 401(k) / Roth 403(b) — already post-tax. Look for "Roth" in the label. Roth contributions go in your taxable wages, not pre-tax.
• Roth IRA — same reason.
• After-tax contributions — voluntary contributions above the 401(k) limit, usually labeled "AT 401k" or "After-Tax".
• Employer match — that's the employer's money, not yours. Don't add it.
• Health insurance premiums — some are pre-tax (most), but most pay stubs already remove them from your displayed taxable wages, so don't double-count. If your stub shows two "Gross" columns ("Total Gross" and "Federal Taxable Gross"), the difference is already accounted for.

How to find the annual number on your pay stub:

1. Open your most recent pay stub.
2. Look in the "Deductions" or "Pre-Tax" column. Each item will show "Current" (this paycheck) and "YTD" (year-to-date).
3. Add up the YTD totals for everything in the "What counts" list above.
4. Annualize it — multiply by (12 / months elapsed). If your most recent stub is dated June 30 (6 months in), multiply by 2. If it's December 15 (~11.5 months in), multiply by ~1.04.
5. Round to the nearest hundred. Enter that number in the calculator's Pre-tax payroll deductions field.

If you're planning ahead (not looking at a stub): use your intended annual contribution. If you've told HR to defer 10% of a $80,000 salary into a traditional 401(k), enter $8,000. If you also max your HSA ($4,150 individual coverage), add it — enter $12,150.

Common mistakes

• Married couples not coordinating. If both spouses claim dependents on Step 3 of their separate W-4s, the employer doubles the credit. Pick ONE W-4 to claim the dependents on (usually the higher earner's).
• Side hustle income forgotten. Your day job withholds on day-job wages only. Side hustle = no withholding by default. Use Step 4(a) or our side-hustle W-4 hack to cover it.
• Not updating after life changes. New baby, marriage, second job, house — all require a W-4 update. There's no annual deadline; submit anytime.
• Confusing credits with deductions. Step 3 dependents are CREDITS (reduce tax dollar-for-dollar). Step 4(b) itemized deductions reduce TAXABLE INCOME (worth your marginal rate × the amount). Credits are stronger.
• Not accounting for spouse's income. If MFJ and both work, leaving Step 2 blank means each employer withholds as if you were single — you'll under-withhold dramatically.

Are you 65 or older? Senior Bonus Deduction

The One Big Beautiful Bill Act added a new $6,000 deduction for filers age 65 or older, on top of the standard or itemized deduction you'd otherwise take. It runs for tax years 2025 through 2028 and then sunsets unless Congress extends it.

Open the "Age 65 or older?" toggle in the calculator above and check the box if it applies. If you're filing jointly and your spouse is also 65 or older, a second checkbox appears so you can claim $12,000 instead of $6,000.

Phase-out at higher incomes. The bonus shrinks by 6 cents for every dollar of AGI above $75,000 (single) or $150,000 (MFJ), and fully disappears at $175,000 single / $250,000 MFJ. The calculator handles this automatically; the "Step 4(b)" output panel shows the remaining bonus after any phase-out.

Where it lands on the W-4. The Senior Bonus shows up on Step 4(b) (Deductions). That's because Step 4(b) is the place where any extra deduction above standard gets recorded so your employer can adjust your withholding for it. If you're also itemizing, the calculator stacks both pieces on Step 4(b) and the displayed value shows both contributions.

When to update your W-4

• Got married, divorced, or separated
• Had a baby or adopted a child
• A child aged past 17 (lose the $2,200 CTC, get the $500 ODC instead)
• Spouse started or stopped working
• Took a second job or started a side hustle
• Bought a house with significant mortgage interest
• Income changed materially (big raise, lost a job)
• Last year's return surprised you — big refund or surprise bill

2025 numbers to know (post-OBBBA)

• Standard deduction: Single $15,750 · MFJ $31,500 · HoH $23,625 (OBBBA bumped these from $15,000 / $30,000 / $22,500 retroactively for 2025)
• Child Tax Credit: $2,200 per child under 17, up to $1,700 refundable (OBBBA permanently bumped the credit from $2,000 starting in 2025)
• Other Dependent Credit: $500 per qualifying other dependent
• CTC/ODC phase-out: begins $200,000 single / $400,000 MFJ AGI ($50 per $1,000 over)
• Senior Bonus Deduction (new, 2025 to 2028): additional $6,000 deduction per filer age 65 or older ($12,000 if MFJ and both spouses qualify). Phases out 6% per dollar of AGI above $75,000 single / $150,000 MFJ, fully gone at $175,000 / $250,000. Use the "Age 65 or older?" toggle in the calculator above to enable it.
• Brackets: 10% / 12% / 22% / 24% / 32% / 35% / 37%
• 401(k) / 403(b) / 457(b) employee limit: $23,500 (under 50) · $31,000 (50+) · $34,750 (60-63 super catch-up)
• HSA limits: $4,300 self-only · $8,550 family · +$1,000 catch-up if 55+
• Health FSA limit: $3,300 · Dependent-care FSA limit: $5,000 (or $2,500 MFS)
• Commuter benefits: $325/month each for transit and parking

Submitting a W-4 mid-year? Use catch-up mode

By default this calculator assumes you're setting withholding up at the start of the year. If you're filing a new W-4 in June, September, or November, that math is wrong: a full-year Step 4(c) number gets averaged across paychecks you've already received, so you under-withhold for the rest of the year.

Flip on "Updating your W-4 mid-year?" at the top of the calculator. Two inputs appear:

• Submission month. When you'll actually hand the W-4 to HR. We use this to figure out how many paychecks are left in the calendar year.
• Federal tax withheld YTD. Find this on your most recent pay stub, usually labeled "Federal Income Tax YTD" or "Fed Withholding YTD". Don't include FICA, Medicare, or state tax.

The calculator then takes your full-year tax owed, subtracts what you've already paid YTD AND what your employer will keep withholding at the default rate for the rest of the year, and divides whatever's left over your remaining paychecks. That's your Step 4(c) catch-up — the EXTRA per-paycheck amount on top of the default. If the math works out to zero or negative, you're already on track or over-withheld; the calculator tells you to leave Step 4(c) blank and projects your refund.

What this calculator doesn't handle

• State withholding — varies wildly by state. File separately with your state if it has income tax. (Pennsylvania and New Jersey notably tax 401(k) contributions even though the federal government doesn't.)
• FICA withholding — Social Security (6.2%) and Medicare (1.45%) come off your gross pay regardless of W-4 settings. Your employer handles them automatically.
• Self-employment tax — if you have substantial 1099 income, see our quarterly tax calculator or SE tax calculator.
• Capital gains — long-term gains use different brackets. See the stock tax calculator.
• Multiple non-spouse jobs — combine wages and use the W-4 worksheet on page 3.