HR and payroll for startups in the United States
Reviewed by Mellow Editorial Team, HR & payroll content team
Startups in the US face the same federal and state employment obligations as any other employer — from day one, not after you hit some employee threshold. Getting payroll and HR foundations right early saves costly corrections later.
Classify workers correctly before you hire
The first decision shapes everything. Workers are either employees (W-2) or independent contractors (1099-NEC). Misclassification is one of the most common — and expensive — startup mistakes.
The IRS looks at behavioral control, financial control, and the nature of the relationship. A contractor who works set hours, uses your equipment, and does core business work is almost certainly an employee under federal and most state standards. California and several other states apply even stricter tests (such as the ABC test) that make it harder to use contractors legitimately.
Getting this wrong means back taxes, interest, penalties, and potential lawsuits. When in doubt, classify as an employee.
Register, withhold, and remit from day one
Before your first payroll run, you need a Federal Employer Identification Number (EIN) from the IRS and a state employer account number in every state where you have employees. This matters because remote-first startups often end up with workers scattered across multiple states, each with its own registration, withholding, and filing requirements.
Federal payroll taxes you must handle on every employee paycheck:
- Federal income tax — withheld based on each employee's Form W-4 elections, applied at progressive rates from 10% to 37%.
- Social Security — 6.2% withheld from the employee, matched by you as the employer, up to the annual wage base.
- Medicare — 1.45% withheld from the employee, matched by you, with no cap. Employees earning above a high-income threshold also owe an additional 0.9% surcharge, which you withhold but do not match.
State income tax follows on top of this. States like Texas, Florida, and Washington have no state income tax, which simplifies payroll there. Others — California and New York prominently — have their own withholding tables, supplemental rates, and local taxes that require separate setup.
You report and deposit these taxes using Form 941 each quarter. You must issue W-2s to all employees — and send copies to the Social Security Administration — by January 31 each year. Contractors who received $600 or more get a 1099-NEC by the same deadline.
Build your HR infrastructure early, not reactively
Employment in the US is generally at-will, meaning either party can end the relationship at any time for any lawful reason. That flexibility is real, but it does not eliminate the need for documentation.
At minimum, have:
- An offer letter that states compensation, classification, and that employment is at-will (where applicable in your state).
- An I-9 on file for every employee — federal law requires you verify employment eligibility within three days of the start date.
- A basic employee handbook covering workplace conduct, anti-harassment policy, and leave expectations. Even a lean handbook sets clear expectations and helps defend against later disputes.
There is no federal requirement for paid vacation or paid sick leave. Several states and cities — California, New York City, and others — do mandate paid sick leave, so check local rules before you assume zero leave obligations.
Non-competes are another area worth attention. California prohibits most non-compete clauses outright. Other states vary in what they enforce. If your team is distributed, a clause that is valid in one state may be unenforceable where the employee actually works.
Scale payroll without adding headcount to run it
Early-stage startups rarely have the volume to justify a dedicated payroll specialist, but the compliance burden is the same regardless of team size. Two practical options:
Payroll software handles tax calculations, direct deposit, and federal and state filings automatically. The main risk is that the software does what you configure — garbage in, garbage out. Someone still needs to own accuracy.
A Professional Employer Organization (PEO) co-employs your staff and takes on much of the compliance burden. PEOs can also give small teams access to benefits (health insurance, 401(k)) that would otherwise be unaffordable or administratively impossible to administer independently. The tradeoff is cost and some loss of direct control over HR processes.
For startups hiring internationally as well as domestically, consolidating payroll into one system from the start reduces the risk of parallel, disconnected processes. See how Mellow runs payroll across six countries on one platform for a practical example of what that looks like.
What to prioritize in the first six months
In rough order of urgency:
1. Get your EIN and state registrations done before any paycheck runs.
2. Collect W-4s and I-9s from every new hire on day one.
3. Confirm worker classification with legal review if you are relying heavily on contractors.
4. Set up a compliant payroll system tied to your deposit schedule — deposits that are late or short trigger automatic penalties.
5. Check state-specific paid leave laws for every location where you have employees.
The compliance landscape in the US is fragmented by design — federal rules set a floor, and states frequently go further. For a startup, the practical approach is to treat compliance as operational infrastructure, not a legal afterthought.
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