When should I update my W-4?

Update your W-4 after: marriage or divorce, birth of a child, buying a home, starting a second job, significant income change, spouse starting or stopping work, and any time your refund was too big (over $1,000) or you owed money at tax time. The goal is to get your withholding as close to your actual tax liability as possible.

What happens if I don't withhold enough taxes?

If your withholding falls too short, you'll owe money when you file your tax return. If you owe more than $1,000, the IRS may charge an underpayment penalty (currently about 7-8% annually on the shortfall). You can avoid the penalty by owing less than $1,000, paying at least 90% of current year's tax, or paying at least 100% of prior year's tax (110% if income exceeds $150,000).

Is a big refund good or bad?

A big refund means you overpaid taxes throughout the year — the IRS held your money interest-free. A $3,000 refund means you gave the government a $250/month interest-free loan. That money could have been in your bank account earning interest, invested, or used to pay down debt. The ideal target is a refund of $0-$500 or a small amount owed.

I Forgot to Update My W-4 — Am I Withholding the Wrong Amount?

If you forgot to update your W-4, use the IRS Tax Withholding Estimator to check if you’re on track — then submit a new W-4 to your employer. It takes 10 minutes and can save you from a surprise tax bill or an unnecessarily large refund.

When You Need to Update Your W-4

Life Event	Update W-4?	Why
Got married	✅ Yes	Filing status and income bracket change
Got divorced	✅ Yes	Filing status changes back to Single
Had a baby	✅ Yes	New dependent = more withholding allowance
Bought a home	✅ Yes	Mortgage interest deduction changes withholding needs
Started a second job	✅ Yes	Combined income may push you into a higher bracket
Spouse started or stopped working	✅ Yes	Household income changed
Got a significant raise	✅ Yes	May need more withholding
Started freelancing/side income	✅ Yes	Or make quarterly estimated payments
Large refund (over $1,000)	✅ Yes	You’re overwithholding — adjust to keep more per paycheck
Owed money at tax time	✅ Yes	You’re underwithholding — increase withholding

How to Check Your Withholding

Step	Action
1	Go to irs.gov/W4App (IRS Tax Withholding Estimator)
2	Enter your filing status, income, and current withholding
3	Tool shows if you’re on track, overwithholding, or underwithholding
4	Follow the tool’s W-4 recommendation
5	Submit the new W-4 to your employer’s HR/payroll

Impact of Common Withholding Mistakes

Scenario	Approximate Annual Impact
Married but withholding as Single	Overwithholding by $2,000-$5,000 (big refund)
Single but withholding as Married	Underwithholding by $2,000-$5,000 (tax bill)
Forgot to add dependent	Overwithholding by $1,000-$2,000 per child
Two earners, no W-4 adjustment	Underwithholding by $2,000-$10,000+
Large raise with no W-4 update	Possible under/overwithholding depending on bracket

The Cost of Overwithholding

Annual Overwithholding	Monthly Money You’re Missing	What It Could Earn (5% HYSA)
$1,200	$100/month	$60/year in interest
$2,400	$200/month	$120/year in interest
$3,600	$300/month	$180/year in interest
$6,000	$500/month	$300/year in interest

How to Submit a New W-4

Step	Detail
1	Download Form W-4 from irs.gov or get it from HR
2	Fill out Steps 1-4 (the new form is simpler than the old one)
3	Submit to your employer’s payroll department
4	Changes typically take effect within 1-2 pay periods
5	Review your next pay stub to confirm new withholding

You can submit a new W-4 at any time — there’s no limit on how often you can update it.

The Bottom Line

Use the IRS Tax Withholding Estimator (irs.gov/W4App) today — it takes 10 minutes and tells you exactly what to enter on your new W-4. Don’t aim for a big refund; aim to break even. Every $1,000 in refund is $83/month you could have had in your paycheck. Update your W-4 any time a major life event changes your tax situation.