What Tax Forms to Fill Out for Employment?
Understand the essential paperwork for new hires, from managing your payroll tax setup to confirming your legal authorization to work in the U.S.
When starting a new job, you must complete several government forms to ensure your employer complies with tax laws and verifies your legal eligibility to work. Completing this paperwork accurately is a standard part of the onboarding process and directly impacts how your pay is processed. Your employer’s human resources department will provide these forms.
Federal Income Tax Withholding (Form W-4)
The primary form for federal taxes is the IRS Form W-4, Employee’s Withholding Certificate, which tells your employer how much federal income tax to withhold from your paycheck. If too little is withheld, you may owe money when you file your annual tax return. If too much is withheld, you are giving the government an interest-free loan until you receive a tax refund.
You must determine your tax filing status, such as “Single or Married filing separately,” “Married filing jointly,” or “Head of household.” Step 1 of the form captures this personal information. If you have a simple financial situation with one job and no dependents, you may only need to complete Step 1 and sign the form in Step 5.
Step 2 is for individuals who hold more than one job or are married filing jointly and their spouse also works. This step helps prevent under-withholding from multiple income sources. You can use the IRS’s online Tax Withholding Estimator or complete the “Multiple Jobs Worksheet” included with the form to calculate an additional amount to withhold.
Step 3 allows you to claim dependents to reduce your withholding for credits like the Child Tax Credit. You will multiply qualifying children under 17 by $2,000 and other dependents by $500. Step 4 is for other adjustments, such as other income, deductions, or any extra tax you want withheld. If you plan to itemize deductions beyond the standard deduction, you can use the “Deductions Worksheet” for a more precise calculation. For 2025, the standard deduction amounts are $15,000 for Single or Married filing separately, $30,000 for Married filing jointly, and $22,500 for Head of household.
State Income Tax Withholding Forms
Most states impose their own income tax, which requires a separate withholding form. The specific forms and rules differ by state. Some states have a unique form, while others may use the federal Form W-4 or a modified version of it.
Your employer will provide the correct form for the state where you work, and they are also available on your state’s Department of Revenue website. The information required mirrors the federal form, asking for personal details, filing status, and any state-specific adjustments.
Employment Eligibility Verification (Form I-9)
Separate from tax documents, you must complete Form I-9, Employment Eligibility Verification. This U.S. Citizenship and Immigration Services (USCIS) form verifies your identity and legal authorization to work in the United States. It is not related to taxes but is a mandatory part of the hiring process. You are responsible for completing the first section of the form.
In Section 1, you will provide your full name, address, date of birth, and Social Security number. You must also attest to your citizenship or immigration status, such as U.S. citizen, lawful permanent resident, or an alien authorized to work. You must complete and sign this section on or before your first day of employment.
You must present original, unexpired documents to your employer to prove your identity and work authorization from the “Lists of Acceptable Documents.” You must provide either one document from List A or a combination of one from List B and one from List C. List A documents, such as a U.S. Passport or Permanent Resident Card, establish both identity and employment authorization.
List B documents establish identity and include a driver’s license or school ID card with a photograph. List C documents establish employment authorization and include a Social Security card or a certified copy of a birth certificate. Your employer cannot specify which documents you must present.
Submitting Your Completed Forms
You will submit the completed forms directly to your employer’s human resources department. Your employer is required to keep these forms on file and make them available for inspection if requested by the IRS or state agencies, but they are not submitted otherwise.
Tax forms should be completed on or before your first day, but Form I-9 has a strict timeline. You must complete Section 1 by your first day of work and present your original documents to your employer within three business days of your start date. Your employer then completes Section 2, certifying they have examined your documents. It is a good practice to keep copies of all submitted forms for your records.