Two paths lead away from doing HR yourself: a PEO and an ASO. Both take work off your plate, but they split responsibilities differently. A PEO (Professional Employer Organization) becomes your co-employer and handles everything from health insurance to tax filing. An ASO (Administrative Services Organization) stays a vendor and runs specific tasks you assign. Picking the wrong model can mean overpaying for services you don’t need or missing coverage your team depends on. This guide breaks down the real differences between a PEO vs ASO so you can choose the right fit.
What Is a PEO?
A PEO partners with your business through a co-employment arrangement. It becomes the employer of record for tax and benefits purposes. Your employees’ W-2s are filed under the PEO’s federal employer identification number (EIN), not yours.
You still run your business day to day. You hire, manage, and direct your team. The PEO handles payroll, tax filing, health insurance, workers’ comp, and HR compliance behind the scenes. For a closer look, see our guide to what a PEO is.
What Is an ASO?
An ASO provides HR support without becoming your co-employer. You stay the sole employer of record. Your EIN stays on every tax filing and W-2.
Think of an ASO as hiring an HR assistant rather than a partner. You pick which services you want (payroll processing, benefits administration, compliance consulting) and the ASO handles those tasks. But you keep full control and full liability. The ASO does not sponsor health plans, carry workers’ comp policies, or file taxes on your behalf.
The Core Difference: Co‑Employment
Co-employment is the dividing line between a PEO and an ASO.
With a PEO, your employees technically have two employers: your company (which directs their day-to-day work) and the PEO (which handles taxes, benefits, and compliance). The IRS recognizes this arrangement, and certified PEOs take on sole federal payroll tax liability under IRC Section 3511 (IRS, 2024).
An ASO has no employer relationship with your employees. It is a service provider. You sign a vendor contract, not a co-employment agreement.
This single difference drives everything else: who files your taxes, who sponsors your health plan, who carries your workers’ comp insurance, and who shares compliance liability.
PEO vs ASO: Side‑by‑Side
| Feature | PEO | ASO |
|---|---|---|
| Employment model | Co-employment (shared) | Vendor (no co-employment) |
| Employer of record | PEO for tax and benefits | You remain sole employer |
| Payroll tax filing | PEO files under its EIN | You file under your EIN |
| Health insurance | Pooled large-group rates | You negotiate your own |
| Workers’ comp | PEO sponsors the policy | You maintain your own |
| Compliance liability | Shared between you and PEO | Stays entirely with you |
| Typical admin pricing | 2–12% of payroll or $40–$160/employee/month | Varies by service selected |
| Best for | Small businesses under 50 employees with no HR staff | Mid-size companies with existing HR capability |
Ranges are illustrative. Actual costs vary by industry, company size, and provider.
The total cost comparison depends on what you need. PEO fees cover more services in a single bill. ASO fees look lower but don’t include benefits or workers’ comp, which you buy separately. For a full list of what a PEO typically covers, see what a PEO does.
Which Model Fits Your Business?
The right answer depends on three things: what your team needs, what you already have in place, and how much control you want to keep.
Choose a PEO when:
- You have fewer than 50 employees and no dedicated HR person
- You want access to large-group health insurance rates your company could not negotiate alone
- You need workers’ comp coverage, especially in a higher-risk industry like construction or manufacturing
- You want someone else handling payroll tax filing and compliance
- You are growing fast and need HR support that grows with you without hiring an internal team
According to NAPEO’s 2024 research, businesses using a PEO grow at more than double the rate of similar non-PEO businesses and are about a third less likely to go out of business in a given year (NAPEO, 2024).
Choose an ASO when:
- You already have at least one HR professional on staff
- You want full control over your EIN, tax filings, and benefits plans
- You have competitive benefits rates through your own broker or buying group
- You prefer picking only the HR services you need rather than paying for a bundle
- Your company is approaching 200 or more employees, where PEO pooling advantages begin to shrink
Not sure which side you fall on? Estimate your PEO costs and then use our PEO ROI calculator to see whether the bundled approach pays for itself.
What Each Model Really Costs
On paper, an ASO looks cheaper, because you pay only for the services you select. But the sticker price hides what the two models include. A PEO administrative fee typically runs $40 to $160 per employee per month, or 2% to 12% of payroll, and that fee covers payroll, tax filing, and HR support while giving you access to the PEO's workers' compensation coverage and pooled benefit plans, whose premiums are billed alongside it. An ASO fee is usually lower, but it rarely includes health insurance or workers' comp; you buy those separately, at rates you negotiate yourself.
So the real comparison is total cost, not line-item cost. A business with no HR staff and no competitive benefits rates often finds a PEO costs less overall once the separately purchased pieces of the ASO model are added up. A business that already has an HR team and strong benefits rates may pay less overall with an ASO. To put real numbers against your own headcount, estimate your PEO costs and compare the bundled figure against what you pay today.
Common Questions
Is an ASO always cheaper than a PEO?
Not once you add everything up. An ASO's fee is typically lower, but it excludes benefits and workers' compensation, which you purchase on your own. A PEO's fee is higher, but it gives you access to both, often at pooled rates a small business could not reach alone. Compare total cost, not the headline fee.
Can I switch from an ASO to a PEO later?
Yes. Many businesses start with an ASO while they have HR capacity, then move to a PEO as they grow or as benefits and compliance get harder to manage alone. The move means adopting co-employment and shifting payroll tax filing to the PEO's EIN, so plan the transition around a quarter or year-end.
Does an ASO provide health insurance?
No. An ASO can administer a health plan you sponsor, but it does not sponsor the plan itself or pool your employees for large-group rates. If access to better benefits is your main reason for outsourcing, that points toward a PEO.
Which model is better for a startup?
It depends on whether you have anyone running HR. A startup with no HR staff and a need for competitive benefits usually gets more from a PEO's bundled model; a startup that already has an HR lead and good benefits rates may prefer the control of an ASO. Businesses that use a PEO also grow faster and fail less often on average (NAPEO, 2024), which matters in the early years.
Do I lose control of my employees under a PEO?
No. Co-employment splits responsibilities on paper, not day-to-day authority. You still hire, manage, assign work, and decide pay and promotions. The PEO handles payroll, tax filing, benefits, and compliance behind the scenes. You direct the people; the PEO handles the paperwork.
The Bottom Line
A PEO and an ASO solve the same problem (HR is eating your time), but they solve it differently. A PEO goes deeper: co-employment, sponsored benefits, shared insurance, and shared compliance risk. An ASO stays a step back: it handles the tasks you assign, and you keep everything in your name.
For most small businesses under 50 employees with no HR staff, a PEO delivers more value per dollar. For mid-size companies with existing HR capability and strong benefits rates, an ASO gives you the admin help without the structural change.
Request a free consultation through our independent broker to compare PEO proposals for your situation. The process takes a few business days and costs you nothing. The consultation is free to you. If you sign through the broker, he shares part of his fee with us. You can also browse our PEO directory to see which providers serve your area.
Sources
- IRS, "Certified Professional Employer Organizations." irs.gov
- NAPEO, "PEO Clients: Faster Growing, More Resilient Businesses with Lower Turnover Rates" (2024). napeo.org
- US Chamber of Commerce, "PEO vs. ASO: Key Factors to Consider" (2024). uschamber.com
- G&A Partners, "ASO vs PEO: Key Differences." gnapartners.com
- ADP, "What Is the Cost of a PEO?" (2026). adp.com
