How do I fill out my US tax forms (W-4)?

Last updated: August 27, 2026

Applies to: US W-2 employees. If you're an independent contractor you complete a W-9 instead (see "How do I fill out my US contractor tax form (W-9)?"), and Canadian employees complete a TD1. Not sure which you are? See "Am I a W-2 employee or an Independent Contractor?"

Summary: As a US W-2 employee you complete a federal Form W-4 and, in most states, a state withholding form during onboarding. Together they tell us how much income tax to withhold from each paycheck. You fill them out and e-sign them right in your Ascen account, and you can update them anytime after you start.

What you complete, and why

  • Federal Form W-4 — sets your federal income-tax withholding based on your filing status, dependents, and any extra amount you choose to withhold.

  • A state withholding form — for states that have an income tax. Some states have no income tax, so you may not see a state form at all. Rules vary by your work location, so what you're asked to sign depends on where you work. (Working in more than one state? See "Working or living in more than one state: how state taxes work.")

Unlike an independent contractor, you do have income tax withheld from each paycheck — the W-4 is how you tell us how much. For what actually comes out of your check once you're paid, see "Understanding the taxes withheld from your paycheck."

Filling them out during onboarding

Your tax forms are part of your onboarding checklist and need to be completed before you start — you won't be able to begin work or submit time until onboarding is finished. There are three short steps:

  1. Enter your withholding information (the "Tax Withholding Information" step). You'll answer the same questions found on a paper W-4 — filing status, dependents, and any additional amount you want withheld. Each field has a "?" you can hover over for a plain-language explanation.
    - Optional but recommended: use the IRS Tax Withholding Estimator — there's a button to it right on this step — to figure out what to enter so your withholding lands close to what you'll actually owe.

  2. Review and sign your federal W-4 (the "Form W-4" step). We generate your W-4 from the information you just entered. Review it, then e-sign by typing your name. If something looks wrong, use the "Something wrong? Update PDF here" link to go back, fix your answers, and regenerate the form.

  3. Sign your state withholding form(s) (the "State Withholding" step). Review and sign a form for each state that requires one. If your work state has no income tax, this step is simply skipped.

Once all applicable forms are signed, your withholding setup is complete.

Changing your withholdings later

Your W-4 isn't a one-time task — you can update it whenever your situation changes (marriage or divorce, a new dependent, a second job, or a large refund or balance due last year). For a fuller list of when and why to revisit it, see "When and why to update your W-4."

To make the change:

  1. Go to your Paychecks page.

  2. Click Update Withholdings in the upper right.

  3. Choose what to update — Federal (W-4), State (then pick the state), or All.

  4. Confirm. You'll be walked back through the same steps as onboarding to enter new values and re-sign the updated form(s).

Your new withholding applies going forward, to paychecks processed after you finish.

Finish the update once you start it. Choosing Update Withholdings reopens that withholding step as an outstanding item on your account, and an outstanding step can hold up access to the rest of your profile — including entering your time — until it is completed and signed. So if you clicked Update Withholdings, left partway through, and then found you were being asked to complete a step again or could not submit your hours, nothing has been reset and your onboarding has not been undone: log back in, finish and re-sign the withholding form you started, and full access returns. If you decide you did not want to change anything after all, you still need to complete the step — re-entering and re-signing your existing values is enough.

Note: If the IRS has issued a lock-in letter for you, your federal withholding is set by that letter and you won't be able to reduce it yourself until the IRS lifts it. If you've been told a lock-in letter applies to you and have questions, contact support.

Viewing or downloading your signed W-4

Your signed federal W-4 (and each state form) is saved to your Ascen account as a signed document. You can download a copy at any time to review it or keep it for your records.

Your year-end W-2 is a separate document that reports what you actually earned and had withheld — for that, see "Where to find your tax documents for the year."

Making sure your withholding is right

We can't give individual tax advice, but two things help:

  • Run the IRS Tax Withholding Estimator before you enter or update your numbers.

  • If you believe there's an actual error on your withholding, contact support — we can help you generate a corrected federal or state form.

The goal is to withhold close to what you'll owe for the year: withhold too little and you may owe a balance (and possibly a penalty) at tax time; withhold too much and you get a bigger refund but have effectively lent that money interest-free all year.

This article is general information, not individual tax advice. For your specific situation, use the IRS estimator or consult a tax professional.

Official references: About Form W-4 (IRS) · Tax Withholding Estimator (IRS)

Related: How do I fill out my tax forms? (overview) · When and why to update your W-4 · Understanding the taxes withheld from your paycheck · Working or living in more than one state: how state taxes work · Where to find your tax documents for the year