Adding starters to payroll in the United States
Reviewed by Mellow Editorial Team, HR & payroll content team
When you hire someone new in the United States, you need to collect specific documents, register information with government agencies, and set up withholding correctly before you run their first paycheck. Miss a step and you risk penalties, incorrect tax deposits, or failed state new-hire reports.
Collect the required paperwork on day one
Two forms are non-negotiable before an employee starts work.
Form I-9 (Employment Eligibility Verification). You must complete Section 1 with the employee on or before their first day, and complete your own Section 2 — verifying original identity and work-authorization documents — within three business days of the start date. Keep the completed I-9 on file; you do not send it to any agency unless audited.
Form W-4 (Employee's Withholding Certificate). The employee fills this out to tell you how much federal income tax to withhold. Federal income tax is progressive, running from 10% to 37% across the brackets. The W-4 captures filing status and any adjustments; your payroll system uses the result together with the IRS withholding tables to calculate the correct amount each pay period. If an employee does not return a W-4, IRS rules require you to withhold as if they are single with no adjustments.
If you operate in a state with its own income tax, collect the equivalent state withholding form at the same time. States such as Texas, Florida, and Washington have no state income tax, so no state withholding form is needed there.
Register the new hire with your state
Every US state requires employers to report new hires to a state agency — typically the state's child support enforcement or labor department — within a set number of days of the hire date. The deadline varies by state, but 20 days is a common maximum. You submit basic information: the employee's name, address, Social Security Number, and your Federal Employer Identification Number (FEIN). States use this data to enforce child support orders and detect unemployment insurance fraud. Most states offer an online portal for this submission.
Set up payroll withholding and employer taxes correctly
Once documentation is in place, configure the employee's record in your payroll system with:
- Federal income tax withholding based on the W-4 elections and current IRS tables.
- FICA taxes. Both you and the employee owe these. The employee side is 6.2% for Social Security (applied up to the annual wage base) plus 1.45% for Medicare with no cap. You match both of those as the employer. High earners also face an Additional Medicare Tax of 0.9% on wages above the relevant threshold — that portion is the employee's obligation only; you withhold it but do not match it.
- Federal Unemployment Tax (FUTA). This is an employer-only cost; nothing is withheld from the employee's wages.
- State unemployment insurance (SUI). Rates vary by state and by your account's experience rating. Again, this is generally an employer cost, not a paycheck deduction.
- Any applicable local taxes — some cities and counties levy their own income or payroll taxes.
If you use a payroll provider or software, assigning the correct work-location state and local tax jurisdiction when setting up the new hire is critical. Errors here compound quickly over pay periods.
Enroll the starter in benefits within eligibility windows
If you offer a group health plan subject to ERISA, new hires typically have a limited enrollment window — often 30 to 60 days from their start date, depending on plan terms. Missing that window means the employee may have to wait until the next open enrollment period. Document the date you provided enrollment materials and keep a record of the employee's election or waiver. The same principle applies to 401(k) or other retirement plans, which may have their own waiting periods and eligibility rules under the plan document.
Prepare for upcoming reporting obligations
Adding a starter creates downstream reporting requirements you need to track from day one.
Form W-2. At year end, you must issue a completed W-2 to each employee and file copies with the Social Security Administration by January 31 following the tax year. The W-2 summarizes all wages paid and all taxes withheld across the year.
Form 941. You file this quarterly to report federal income tax withheld and FICA taxes for all employees. Payroll tax deposits (via the Electronic Federal Tax Payment System) are due more frequently — either monthly or semi-weekly depending on your deposit schedule.
Getting the new-hire setup right the first time keeps your deposit schedule accurate, avoids IRS notices for under-withholding, and ensures the employee's tax records reflect reality when they file their own return. For businesses managing workers in multiple states or countries, a consistent onboarding checklist matters even more — how Mellow runs payroll across six countries covers what that looks like in practice.
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