How do I know if I am withholding too much or too little?

The IRS Withholding Estimator (irs.gov/W4app) compares your projected withholding to your expected annual tax liability. If your projected refund is more than $1,000, you are likely over-withholding. If you are projected to owe more than $1,000, you are likely under-withholding (and may face an underpayment penalty).

What happens if I never update my W-4?

Your 2020 or pre-2020 W-4 remains in effect until you change it. If your situation has not changed significantly, this is usually fine. However, life changes (marriage, children, job changes, income changes, home purchase) that affect your tax liability without a corresponding W-4 update will result in incorrect withholding.

Can I correct a paycheck error after the fact?

Yes — payroll errors can be corrected. For the current year: contact your employer’s payroll department immediately with documentation. They can adjust the error on a future check. For prior year errors: if they affect your W-2, you need an amended W-2 (W-2C). You may also need to file Form 1040-X to amend your return if a prior year W-2 was incorrect.

Is it better to owe a small amount at tax time or get a small refund?

Both are acceptable, but owing a small amount (under $1,000) or getting a small refund (under $1,000) represents accurate withholding. A refund under $1,000 is fine — you get a small amount back without having withheld excessively. Owing under $1,000 is also fine as long as you meet the safe harbor (paid at least 90% of current year tax or 100% of prior year tax).

Should I increase my 401(k) if I have a large tax refund?

Yes — if you are consistently over-withholding, consider redirecting the excess withholding to your 401(k). Update your W-4 to reduce withholding by the annual refund amount ÷ 26 (biweekly), then increase your 401(k) contribution by a similar amount. This converts a zero-interest IRS loan into tax-advantaged retirement savings.

Paycheck Mistakes to Avoid: 8 Common Errors That Cost You Money

Paycheck mistakes are often invisible until tax time — and some cost hundreds or thousands of dollars per year in unnecessary taxes, missed deductions, or benefit coordination errors. Here are eight of the most common and costly paycheck-related mistakes, with practical fixes.

Mistake 1: Never Updating Your W-4

Your W-4 stays on file indefinitely — if you filed it when you were single and are now married with a child, your withholding is almost certainly wrong. Major life events (marriage, divorce, new child, home purchase, second job) require W-4 updates. An outdated W-4 causes either over-withholding (interest-free loan to the IRS) or under-withholding (tax bill plus potential penalty).

Mistake 2: Not Maximizing Pre-Tax Benefits

Failing to enroll in available pre-tax benefits (FSA, HSA, commuter benefits, additional 401k if employer allows) leaves tax savings on the table. Every pre-tax dollar saves your marginal rate. At 22% federal + 5% state, every $1,000 of pre-tax contributions saves $270 in income taxes. Many workers leave $500-$2,000+ in annual tax savings unclaimed by not maximizing pre-tax elections.

Common paycheck mistakes and their typical annual cost

Common Paycheck Mistake	Typical Annual Cost	Fix
Wrong W-4 filing status (single vs. married)	$500-$2,000 in wrong withholding direction	Update W-4 immediately at each life change
Not enrolling in FSA for known medical expenses	$200-$700 in unnecessary taxes	Elect FSA during open enrollment for predictable healthcare costs
Choosing lower HSA contribution when eligible	$100-$650 in missed FICA savings	Maximize HSA via payroll for triple tax advantage
Ignoring pay stub errors	Varies — can be hundreds to thousands	Review every pay stub; dispute errors immediately
Not noting SS wage base cap date	Missing the cash flow benefit	Watch for September-October when cap is hit
Roth 401k vs Traditional without analysis	$500-$2,500 in take-home lost	Compare Roth vs Traditional based on your bracket
Not calculating state + local taxes before relocating	$2,000-$15,000 more in taxes	Use take-home calculator with each state before deciding

🔑The Most Expensive Mistake: Ignoring the Annual Review

Not reviewing your withholding and benefit elections annually costs many workers $500-$3,000/year in missed tax savings or wrong withholding. Use your tax return filing time each spring as a trigger to: (1) review your W-4 elections, (2) plan benefit elections for the upcoming open enrollment, and (3) calculate expected tax liability for the coming year.

Mistake 8: Treating a Tax Refund as Good Financial Planning

A large federal tax refund means you over-withheld — you gave the IRS a zero-interest loan all year. The average 2024 federal refund was approximately $3,167. Had that been invested monthly throughout the year at a HYSA rate of 4.75%, you would have earned approximately $75 in interest. Adjust your W-4 to receive that money in your paycheck each month and invest it yourself.

Verify Your Withholding Is Correct

Calculate your expected take-home pay to check whether your current W-4 is producing the right withholding amount.

Open Take-Home Pay Calculator →

Paycheck Mistakes to Avoid: 8 Common Errors That Cost You Money

Mistake 1: Never Updating Your W-4

Mistake 2: Not Maximizing Pre-Tax Benefits

Mistake 8: Treating a Tax Refund as Good Financial Planning

Frequently Asked Questions

Frequently Asked Questions

More Take-Home Pay Guides

How to Use a Take-Home Pay Calculator: Complete Guide

How Federal Income Tax Withholding Works: A Complete Explanation

How FICA Taxes Work: Social Security and Medicare on Your Paycheck