Every January, your employer sends you a little form called a W-2. It shows up in your mailbox or your HR portal, and for most people, the reaction is the same: a quick glance at the big number, a vague sense of confusion about everything else, and then it gets stuffed into a folder until tax time.
But your W-2 is actually one of the most important financial documents you receive each year. It tells you — and the IRS — exactly how much you earned, how much tax was withheld, how much went to Social Security and Medicare, and a lot more. Understanding it can help you spot errors, plan your taxes better, and make smarter decisions about things like retirement contributions and benefits.
So let us go through the key boxes, one by one, in plain English.
The Basics: Boxes a Through f
These are the identification boxes at the top of the form. They contain your personal information and your employer's details:
- Box a: Your Social Security number
- Box b: Your employer's Employer Identification Number (EIN)
- Box c: Your employer's name, address, and ZIP code
- Box d: A control number (used for internal processing — you can ignore this)
- Box e: Your name
- Box f: Your address
Quick tip: always double-check that your name and Social Security number are correct. A mismatch between your W-2 and your tax return can delay your refund or cause issues with the IRS. If something is wrong, contact your employer's payroll department right away.
Box 1: Wages, Tips, and Other Compensation
This is the number most people look at first. Box 1 shows your total taxable wages for the year. But here is the thing — it is usually not the same as your total salary.
Why? Because Box 1 is your gross pay minus pre-tax deductions. Things like your 401(k) contributions, health insurance premiums (if you pay them pre-tax), HSA contributions, and FSA contributions all reduce the number in Box 1. So if you earned $70,000 but contributed $6,000 to your 401(k) and $3,000 to health insurance, Box 1 would show $61,000.
This is the number you use when filing your federal income tax return. You can check how much tax you owe on this amount using our income tax calculator.
Box 2: Federal Income Tax Withheld
This shows how much federal income tax your employer took out of your paychecks throughout the year. When you file your tax return, this amount is compared against what you actually owe. If too much was withheld, you get a refund. If too little was withheld, you owe the difference.
If you consistently get a huge refund (over $1,000), it means you are having too much withheld — which is basically giving the government an interest-free loan. Consider adjusting your W-4 to keep more money in each paycheck throughout the year. On the other hand, if you owe a big amount every April, you might want to increase your withholding so you do not get hit with a surprise bill.
Boxes 3, 4, 5, and 6: Social Security and Medicare
These four boxes cover your FICA taxes — the combination of Social Security and Medicare:
- Box 3: Social Security wages — the amount of your pay subject to Social Security tax. For 2025, this is capped at $176,100.
- Box 4: Social Security tax withheld — should be 6.2% of Box 3.
- Box 5: Medicare wages — usually the same as or close to your total earnings (there is no cap for Medicare).
- Box 6: Medicare tax withheld — should be 1.45% of Box 5. If you earn over $200,000, you will also see an additional 0.9% Medicare surtax.
Notice that Box 3 might be different from Box 1. That is because 401(k) contributions reduce your income tax wages (Box 1) but not your Social Security wages (Box 3). So you still pay Social Security tax on 401(k) contributions — you just do not pay income tax on them until withdrawal.
Want to see how FICA taxes affect your paycheck? Our payroll calculator breaks it all down.
Box 7: Social Security Tips
This box only applies if you received tips and reported them to your employer. If you work in a restaurant, bar, or hotel, any tips you reported will show up here. The total of Box 3 and Box 7 should not exceed the Social Security wage base ($176,100 for 2025).
If you earn tips, you might also find our tip tax calculator helpful for understanding how your tips are taxed.
Box 10: Dependent Care Benefits
If your employer offers a dependent care FSA (Flexible Spending Account) and you contribute to it, the amount will show here. The maximum for 2025 is $5,000 per household. This money is not included in your taxable wages in Box 1, which saves you both income tax and FICA taxes.
Box 12: Codes That Confuse Everyone
Box 12 is where things get a little alphabet-soup-like. It uses letter codes to report various types of compensation and deductions. Here are the most common ones you will see:
- Code D: 401(k) contributions — the amount you put into your traditional 401(k) during the year.
- Code AA: Roth 401(k) contributions — if your employer offers a Roth option and you used it.
- Code DD: Cost of employer-sponsored health coverage — this is for informational purposes only. It is not taxable income. It just shows the total cost of your health insurance (both your share and your employer's share).
- Code E: 403(b) contributions (similar to a 401(k) but for nonprofits and government employees).
- Code W: HSA contributions made by your employer (including amounts you contributed through payroll deduction).
Code DD is the one that freaks people out the most. They see a number like $18,000 and think they owe taxes on it. You do not. It is purely informational.
Box 13: Checkboxes
Box 13 has three checkboxes:
- Statutory employee: If this is checked, you are treated as an employee for Social Security and Medicare but as self-employed for income tax purposes. This is uncommon.
- Retirement plan: If this is checked, it means your employer offered you a retirement plan during the year. This can affect your ability to deduct traditional IRA contributions.
- Third-party sick pay: Checked if you received sick pay from a third-party insurer. Most people will not see this checked.
Boxes 15–20: State and Local Taxes
The bottom section of your W-2 covers state and local taxes. You might see up to two states listed here if you worked in multiple states during the year.
- Box 15: Your state and your employer's state tax ID number
- Box 16: State wages — may differ from Box 1 due to state-specific rules
- Box 17: State income tax withheld
- Boxes 18–20: Local wages and local taxes withheld, if applicable
If you live in a state with no income tax — like Texas, Florida, or Nevada — these boxes may be empty. Curious about how different states compare? Our state tax comparison calculator lets you see the difference at a glance.
What to Do If Something Looks Wrong
Errors on W-2s are more common than you might think. Maybe your employer used the wrong Social Security number, or maybe your 401(k) contributions do not match your records. Here is what to do:
- Compare Box 1 against your final pay stub of the year — they should be close (the pay stub might include December wages not yet processed, so minor differences are normal).
- Verify your 401(k) contributions in Box 12, Code D against your retirement account statements.
- Check that your Social Security number and name are correct.
- If anything is wrong, contact your employer's payroll or HR department and ask for a corrected W-2 (called a W-2c).
Understanding your W-2 is one of those things that seems overwhelming at first but is actually pretty straightforward once you know what each box means. If you want to see how all these numbers translate into your actual take-home pay, run your salary through our salary calculator — it breaks down federal, state, Social Security, and Medicare taxes so you can see exactly where your money goes.