Should You Still Claim 0 or 1 on Your W-4? Post-Allowance Rules

You no longer choose between claiming 0 or 1 on your W-4. The IRS eliminated withholding allowances in 2020, so the current form doesn’t ask for a number at all. The equivalent choices now live in Steps 2 through 4, where you enter actual dollar amounts for credits, extra withholding, other income, and deductions.¹ If your instinct is to “claim 0” for a bigger refund or “claim 1” for a bigger paycheck, that logic still applies. You just express it differently on the form.

Why Allowances Disappeared

Before 2020, each allowance you claimed was tied to a personal exemption that reduced your taxable income by a fixed dollar amount. Claiming zero meant no reduction and maximum withholding. Claiming one, two, or more reduced withholding by the value of each exemption.

The Tax Cuts and Jobs Act set the personal exemption to zero starting in 2018. That left the allowance count attached to nothing, so the IRS rebuilt the W-4 from scratch for 2020, replacing the allowance number with specific dollar entries.²

One holdover matters. If you filled out a W-4 before 2020 and haven’t updated it or changed jobs since, your old allowance selection is still in effect. Employers are not required to make you fill out the new form, and the old one remains valid indefinitely.³ If your income, marriage, or family situation has shifted since then, an updated form will usually land closer to your real tax bill than the old allowance math ever did.

What “Claiming 0” Looks Like on Today’s W-4

If your goal was maximum withholding and a fat refund, the modern equivalent is straightforward. Complete Step 1 with your personal information and filing status, sign Step 5, and skip the rest. Your employer will withhold based on the standard deduction for your filing status with no downward adjustments, which is the closest the new form comes to the old “claim 0” default.

Want to withhold even more? That’s what line 4(c) is for. Enter a flat dollar amount and your employer will take that much extra federal tax out of every paycheck on top of the normal calculation.² Line 4(c) is the blunt instrument in the current system. If you want a bigger refund and don’t care about optimizing your paycheck, a round number here does the job without any bracket math.

If you never submit a W-4 at all, your employer defaults to withholding as though you’re a single filer with no other adjustments, which typically pulls out more than necessary.³ That’s roughly the old “claim 0” outcome by accident.

What “Claiming 1 or More” Looks Like on Today’s W-4

The old reason for claiming a higher number was to reduce withholding, usually because you had dependents, deductions, or credits the default calculation ignored. Two places on the current form do that work.

Step 3: Dependent Credits

Step 3 reduces your withholding by accounting for tax credits you expect to claim. For 2026, you multiply each qualifying child under 17 by $2,200 and put the total on line 3(a). Other dependents who don’t qualify for the child tax credit are worth $500 each on line 3(b).² You enter a dollar amount, not a count, so the old habit of adding “1 for each kid” doesn’t translate directly.

The child tax credit begins phasing out at $400,000 of combined income for married couples filing jointly and $200,000 for other filers. If you’re near or above those thresholds, entering the full credit amount will under-withhold you, because you won’t actually receive the full credit at filing.

Line 4(b): Deductions Above the Standard

If you plan to itemize and your total itemized deductions will exceed the standard deduction for your filing status, enter the difference on line 4(b). Your employer already builds the standard deduction into the default calculation, so only the amount above it belongs here. Skip this line if you take the standard deduction.²

Line 4(a) works in the opposite direction. If you expect untaxed income like interest, dividends, or retirement distributions, entering it here raises your withholding to cover the tax on it. Don’t include self-employment income on this line, because line 4(a) only covers income tax and self-employment income also triggers Social Security and Medicare tax the line won’t capture. For side income, the IRS points you to its Tax Withholding Estimator at irs.gov/W4App, which produces a single additional withholding figure for line 4(c) covering both taxes.²

The Step Where Most Couples Get Burned

Step 2 is where the biggest under-withholding problems start, and it’s the one situation the old allowance system handled especially poorly. If you hold two jobs, or you’re married filing jointly and your spouse also works, each employer withholds as if its paycheck is your only income. Each one starts the tax calculation at the bottom of the bracket ladder, and your combined income ends up under-withheld because the higher brackets never get counted.

The form gives you three fixes:²

Use the IRS Tax Withholding Estimator at irs.gov/W4App. It calculates a specific dollar amount to enter on line 4(c) of just one of your W-4s. Your other employer sees nothing.
Use the Multiple Jobs Worksheet on page 3 of the form. It produces a similar result on paper, and again the extra withholding goes on line 4(c) of a single W-4.
Check the box in Step 2(c). This is the easiest option, but you have to check it on every W-4 in the household, and it works best when the two jobs pay roughly the same amount. Both employers see the checked box, so it doesn’t hide a second income.

If you’d rather your employer not know about a second job or a working spouse, the estimator and worksheet routes keep that private, since the extra dollars on line 4(c) reveal nothing about where the number came from.³

When to Revisit the Form

Any meaningful change to your income, family, or deductions is a reason to redo your W-4. Common triggers include:

Getting married or divorced
Having or adopting a child
Starting or leaving a second job, or your spouse starting or leaving work
A significant shift in deductions or credits, like buying a home or paying off a mortgage

Nothing forces you to update after a life event, but ignoring a big one nearly always leads to owing money or over-withholding. A new baby is $2,200 in child tax credit your paycheck isn’t reflecting. A spouse’s new job pushes your household into higher brackets that neither employer is calculating for.

Once you submit a revised W-4, your employer must put it in place no later than the start of the first payroll period ending on or after 30 days from when they received it.⁴ Most payroll departments move faster, but a mid-year adjustment won’t hit your next check automatically.

What Getting It Wrong Actually Costs

Over-withholding gets refunded, so it feels harmless. During the 2025 filing season, the average refund was $3,116.⁵ That’s roughly $260 a month those taxpayers didn’t have available to earn interest, pay down debt, or cover bills. Treating your W-4 as a savings account is a zero-interest loan to the Treasury.

Under-withholding is more expensive. If you owe less than $1,000 at filing, you just pay the balance. Beyond that, the IRS charges an underpayment penalty calculated at the federal short-term rate plus three percentage points, which comes to 7% annually as of early 2026.⁶

You’ll generally avoid the penalty if any of these are true:

You owe less than $1,000 after withholding and credits.
You paid at least 90% of this year’s tax liability through withholding.
You paid at least 100% of last year’s total tax through withholding.

The 100% threshold rises to 110% if your adjusted gross income last year was over $150,000, or $75,000 if married filing separately.⁷

So the honest translation of the old question is this. If you liked claiming 0, do nothing beyond Step 1 and Step 5, and add a dollar amount on line 4(c) if you want to push withholding higher. If you liked claiming 1 or more because of dependents or deductions, use Step 3 for credits and line 4(b) for deductions above the standard. And if you have a second job or a working spouse, Step 2 is not optional. That’s the part the old single-number system never handled, and it’s the part most likely to bite you at filing time.

1
Internal Revenue Service. About Form W-4, Employee’s Withholding Certificate
2
Internal Revenue Service. Form W-4 (2026) Employee’s Withholding Certificate
3
Internal Revenue Service. FAQs on the 2020 Form W-4
4
Internal Revenue Service. Form W-4, Employee’s Withholding Certificate
5
Internal Revenue Service. Filing Season Statistics for Week Ending April 4, 2025
6
Internal Revenue Service. Quarterly Interest Rates
7
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty