How to Fill Out Tax Forms for Work: W-4 and W-9

Starting a new job usually means filling out either Form W-4 or Form W-9 before your first paycheck. If the company hired you as an employee, you’ll fill out a W-4 so the right amount of federal income tax comes out of each check. If you’re being paid as an independent contractor, you’ll fill out a W-9 so the company can report what it pays you to the IRS. Learning how to fill out the tax forms for work, W-4 and W-9, comes down to a handful of specific lines on each form and knowing which one applies to you.

Which Form Applies to You

The company that hired you decides your classification, and the IRS looks at three factors to test whether that classification is correct: behavioral control over how you do the work, financial control over how you’re paid and who supplies tools, and the nature of the relationship, including benefits and any written contract.¹

If the company sets your schedule, provides your equipment, and offers benefits, you’re an employee and need a W-4. If you set your own hours, use your own tools, and invoice for finished work, you’re a contractor and need a W-9. The distinction changes your tax bill, too: employees split payroll taxes with their employer at 7.65% each, while contractors pay the full 15.30% themselves as self-employment tax.²

How to Fill Out Form W-4

The W-4, officially the Employee’s Withholding Certificate, tells your employer how much federal income tax to withhold from each paycheck. Download the current version from IRS.gov. Before you start, have your Social Security number, your most recent tax return if you have one, and a rough estimate of your household’s total income for the year. Knowing whether your spouse works and how many dependents you’ll claim makes the rest go quickly.

Step 1: Personal Information

Enter your full legal name, home address, and Social Security number. Check the box for your filing status: single, married filing jointly, married filing separately, or head of household. This choice controls the tax tables your employer uses, so the wrong box throws off every paycheck. Head of household applies if you’re unmarried, pay more than half the cost of keeping up your home, and have a qualifying person living with you.

Step 2: Multiple Jobs or a Working Spouse

Complete Step 2 if you hold more than one job or you’re married filing jointly and your spouse also works. Skipping it when it applies is the single most common reason people end up owing at tax time. You have three options: use the IRS Tax Withholding Estimator online, which is the most accurate; fill out the Multiple Jobs Worksheet that comes with the form; or check the box in Step 2(c) if there are only two jobs total and the pay is roughly similar. The checkbox is blunt because it raises withholding at both jobs, but it beats ignoring the step.

Step 3: Dependent Credits

If your total income will be $200,000 or less, or $400,000 or less for married filing jointly, claim your dependent credits here. For 2026, multiply the number of qualifying children under 17 by $2,200, multiply other dependents by $500, and enter the total.³ Doing this reduces the tax pulled from each paycheck rather than making you wait for a refund.

Step 4: Other Adjustments

Step 4 has three optional lines. Line 4(a) is for other income you expect that won’t have taxes withheld, such as interest, dividends, or retirement distributions; entering an amount here spreads the extra withholding across your paychecks. Line 4(b) is for deductions beyond the standard deduction if you plan to itemize. Line 4(c) lets you ask for a flat extra dollar amount to be withheld from every paycheck, which helps if you’ve owed in past years.

Step 5: Sign and Date

Sign and date the bottom. Your signature certifies the information under penalty of perjury, and once you hand the form in, your employer is required to use it for future payroll calculations.⁴

Claiming Exempt, or Not Turning In a W-4 at All

If you had no federal income tax liability in 2025 and expect none in 2026, you can claim exemption from withholding.³ This usually applies to students, part-time workers, or anyone whose income falls below the standard deduction. To claim it, complete Steps 1(a), 1(b), and 5, write “Exempt” in the space below Step 4(c), and skip the rest. Exempt W-4s expire every year, so you have to file a new one by February 15 of the following year to keep the exemption in place.⁵

If you never turn in a W-4 at all, federal law tells your employer to withhold as if you’re single or married filing separately with no adjustments on Steps 2 through 4.⁵ That’s the most aggressive default. You may get a large refund, but you’ve essentially loaned the government money interest-free all year.

How to Fill Out Form W-9

Form W-9 is the tax form for independent contractors, freelancers, and anyone receiving non-employment income from a business. It doesn’t trigger any withholding on its own. It gives the paying company the information it needs to report your payments to the IRS on a 1099-NEC at year-end. For 2026, that reporting kicks in when a company pays you $2,000 or more during the year.⁶

Lines 1 Through 4: Name and Entity Type

On Line 1, enter your legal name exactly as it appears on your federal tax return. If you do business under a different name, put the trade name or DBA on Line 2. On Line 3, check the box for your federal tax classification. Most solo freelancers check “Individual/sole proprietor.” If you’ve formed a business entity, check the matching box for C Corporation, S Corporation, Partnership, or LLC, and if you’re an LLC, enter a letter code (C, S, or P) showing how the LLC is taxed.⁷ Line 4 is for exempt payee codes and most individuals leave it blank.

Part I: Taxpayer Identification Number

Enter your Social Security number, or your Employer Identification Number if you have one. Sole proprietors with an EIN can use either. The name on Line 1 has to match whichever number you use, because a mismatch is the top cause of problems later.⁷

Part II: Certification and Signature

Signing the form certifies four things: your TIN is correct, you’re not subject to backup withholding, you’re a U.S. person, and any FATCA codes are correct. The backup withholding certification is where people slip up. If the IRS has previously notified you that you’re subject to backup withholding for failing to report interest or dividends, you must cross out that part of the certification before signing.⁷

What Backup Withholding Costs You

If you don’t provide a TIN, or the name and number you provide don’t match IRS records, the company paying you must withhold 24% of your payments and send that to the IRS.⁷ You can claim the 24% as a credit when you file, but it’s a cash-flow problem in the meantime.

When a mismatch shows up, the IRS notifies the payer through its “B” Notice program. A first B-Notice means you need to send a corrected W-9. A second B-Notice within three years is more work: you’ll need to provide a copy of your Social Security card or an IRS verification letter (Letter 147C) confirming your name and number.⁸ The best defense is checking that the name and TIN on your W-9 match your Social Security card exactly before you turn it in.

When to Update Your W-4

Federal regulations require you to submit a new W-4 within 10 days of any life change that reduces the withholding allowances or credits you’ve been claiming.⁴ The common triggers are divorce, a child turning 17 (which ends the child tax credit for that dependent), a spouse losing a job, or picking up a second job. The 10-day rule applies to changes that increase your tax; changes that decrease it, like gaining a dependent, can be filed whenever you like.

Even without a life event, reviewing your W-4 once a year after doing your taxes is the easiest way to avoid either owing money in April or having too much pulled from each check.

Two Other Forms You May See on Day One

The W-4 and W-9 are federal income tax forms. Two other forms often land on the same stack of new-hire paperwork and are not substitutes for either one.

The first is Form I-9, which every new employee in the United States must complete to verify identity and work authorization. It comes from U.S. Citizenship and Immigration Services rather than the IRS. You complete Section 1 on or before your first day, and your employer has three business days from your start date to review your documents and finish Section 2.⁹ You choose which documents to present from the approved lists: one document from List A covers both identity and work authorization, or one from List B plus one from List C.¹⁰

The second is a state withholding form. The W-4 only handles federal income tax. Some states accept the federal W-4 for state withholding, and others have their own version. Your employer’s payroll department will tell you which one your state uses. Nine states have no state income tax and require no state withholding form at all.

1
Internal Revenue Service. Worker Classification 101: Employee or Independent Contractor
2
Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet
3
Internal Revenue Service. Form W-4 (2026) Employee’s Withholding Certificate
4
eCFR. 26 CFR 31.3402(f)(2)-1 Furnishing of Withholding Allowance Certificates
5
Internal Revenue Service. Topic No. 753, Form W-4, Employees Withholding Certificate
6
Internal Revenue Service. 2026 Publication 1099
7
Internal Revenue Service. Form W-9 (Rev. March 2024) Request for Taxpayer Identification Number and Certification
8
Internal Revenue Service. Backup Withholding “B” Program
9
E-Verify. Form I-9 and E-Verify
10
U.S. Citizenship and Immigration Services. Form I-9 Acceptable Documents