PEO vs ASO vs HRO: Which One Fits a Philadelphia Company?

What is a PEO?

A PEO is a professional employer organization. When you sign with one, it becomes your co-employer. That is the single fact that separates a PEO from every other option in this guide.

Co-employment means two companies share the employer role for the same people. You still hire, manage, schedule, and fire. You still set pay and decide who gets promoted. The PEO takes on the employer-of-record duties for payroll and benefits, and it shares certain legal responsibilities that come with them.

The clearest sign of co-employment is the tax ID. The U.S. Chamber of Commerce’s CO- publication explains that a PEO files payroll taxes under its own EIN, the federal employer identification number the IRS uses to track a business. Your employees’ wages are reported under the PEO’s number, not yours. Their W-2s carry the PEO’s name.

That structure has three practical effects.

First, benefits. Because the PEO is the employer of record for thousands of workers across many client companies, it can offer health insurance and retirement plans under its own master plans. Your 12 or 40 employees join a much larger pool. For a company that cannot get affordable group coverage on its own, this is the strongest reason to choose a PEO, and it is a real one.

Second, workers’ compensation. Under a PEO, your employees are usually covered under the PEO’s workers’ comp policy rather than one you buy on your own.

Third, shared liability. Since the PEO is a legal employer, it carries some of the risk if payroll taxes are filed late. If you go this route, ask whether the PEO is IRS-certified. The IRS runs a voluntary certification program under section 7705 of the Internal Revenue Code, and a Certified PEO is solely liable for federal employment taxes on the wages it pays your worksite employees. The IRS publishes a public list, so verify any “certified” claim there.

The trade-off is control and identity. You are handing over your payroll tax identity, your benefit plan choices, and your name on the paycheck. Your people become, on paper, employees of a company they have never heard of. Many small companies accept that for the benefits pool. Some find it a strange thing to explain to a new hire.

The model is well established. NAPEO, the National Association of Professional Employer Organizations, is the PEO industry’s trade and advocacy body, so read its figures with that in mind. According to NAPEO’s industry overview, there are roughly 500 PEOs in the United States serving 233,000-plus client businesses and 5.4 million worksite employees. The same overview reports that PEO clients see 12 percent lower turnover and are 50 percent less likely to go out of business than comparable companies without one. These are association numbers, not independent audits. They tell you the model is large. They do not tell you whether it fits your company.

What is an ASO?

An ASO is an administrative services organization. It is the narrowest of the three. An ASO runs payroll and prepares the tax forms. It also tracks time off and processes the paperwork of onboarding. CO- describes it plainly: the ASO runs payroll under your EIN, and you keep the liability. There is no co-employment.

That is the whole job. An ASO processes. It does not recruit. It does not sit in the room when a manager needs to handle a difficult conversation, design a compensation band, write a handbook that fits your culture, or decide how to structure a team that is about to double. Those are HR judgment calls, and an ASO is not built to make them.

Because of that, an ASO assumes you already have someone inside the company who owns HR. The ASO takes the administrative load off that person’s desk. If you do not have that person, an ASO leaves a gap exactly where a growing company gets hurt: hiring, managing, and keeping people.

An ASO is a good fit for a narrow situation. You have an HR lead, you have a benefits broker and plans you like, and you want the payroll paperwork done by someone else under your own name. If that describes you, it works. If you are a founder with 15 people and nobody in HR, it does not solve your problem.

What is HRO, and how is it different from both?

HRO stands for human resources outsourcing. Done fully, it means an outside firm runs your HR and payroll department for you. Not part of it. The department.

Here is what that looks like in practice. The HRO firm handles payroll and the filings behind it, including Pennsylvania’s local earned income tax and the Philadelphia wage tax. It runs recruiting, from writing the job description to screening to the offer letter. It handles onboarding, handbooks, benefits administration, leave, compliance, performance issues, and the questions employees bring to HR every week. It brings senior HR judgment to the founder or the leadership team when they need it.

What does not change is ownership. You stay the employer. Your EIN is on the payroll. Your name is on the paycheck and the W-2. Your benefit plans are yours. There is no co-employment and nothing to unwind if you ever change your mind. To your employees, the HR team is simply your HR team. They do not see the seam.

That is the difference from a PEO: you keep the employer role instead of sharing it. And it is the difference from an ASO: you get the whole function, including recruiting and HR judgment, instead of just the processing.

HRO is built for two kinds of companies. The first is the startup or growing business that has no HR department yet and does not want to hire one person to do six jobs badly. HRO becomes the department on day one. The second is the company that already has an HR person or a small team. There, the HRO firm works alongside them, taking on recruiting, payroll, and compliance so the in-house lead can focus on the people work that needs to stay close to the business.

One note on definitions, because you will run into a narrower one. CO- describes HRO as the fit for companies that already have HR staff and want to extend the function. Its example is a company moving past 100 employees. That is one version of HRO, and some firms only offer that version. The full-department model described above is how RX2 Solutions runs its HR outsourcing practice, and it is the version that matters for a 10-person company with nobody in HR. When a firm offers you “HRO,” ask which one they mean.

The key question for any offer is simple: does it change who your employer of record is? If yes, it is a PEO, whatever the brochure says. If no, ask whether it includes recruiting and HR judgment or only payroll processing. That tells you whether you are looking at HRO or an ASO.

Which one fits at 5, 25, 50, and 100 employees?

Headcount is not the only factor, but it is the one most companies start with. CO- offers rough fit guidance, and it tilts toward PEOs at small sizes because it assumes HRO only comes in the extend-your-existing-team version. Once the full-department model is on the table, the picture changes. Treat these as starting points, not rules.

At 5 employees. You have no one in HR. You may be running payroll yourself or through a bookkeeper. CO- puts a company this size in PEO territory, at roughly 50 or fewer employees with no in-house HR. The honest question is whether you need the PEO’s benefits pool. If you cannot get affordable group health coverage any other way, that is a real reason to choose one. If you can, HRO gives you a full HR and payroll function at this size without giving up your EIN or your name on the paycheck, and it handles the local tax filings that trip up companies in this region.

At 25 employees. This is where the choice gets real, because this is where hiring becomes constant and management problems start. CO- says an ASO fits at 25 or more when you have at least one HR person. If you have that person and only want paperwork off their desk, an ASO does that. If you have no one in HR, or you have one person drowning, HRO is the fit: it recruits, runs payroll, and handles compliance while your one HR person, if you have one, keeps the culture and the relationships.

At 50 employees. You are at the upper edge of CO-‘s small-company PEO example (50 or fewer employees), though its PEO vs ASO article runs the PEO range up to about 100. Companies at this size start to feel a percent-of-payroll fee, and they want more say over benefit design than a master plan allows. Fifty is also where FMLA, the ACA employer mandate, and Philadelphia’s commuter benefit arrive. HRO carries you through that line without a structural change. A PEO at 50 still makes sense for one reason: you are staying for the benefits pool and you know it.

At 100 employees. CO- describes HRO at this size as the fit for companies with existing HR staff. Its example is a company moving past 100 employees, nearing $2 million in annual payroll, with 2 or more people in HR. That version is real and it works. The full-department version works here too; the question becomes what to keep in-house and what your HRO partner runs. Leaving a PEO at this point is common, because your own buying power is now large enough to get comparable benefits directly.

A note for companies anywhere in greater Philadelphia. Whatever size you are, ask any vendor how it handles the Philadelphia wage tax, Pennsylvania’s local earned income tax under Act 32, and, if you have people across the river, New Jersey and Delaware rules. National providers handle these differently, and the details matter more here than in most metro areas.

What does each cost?

The three models are priced in different ways, and that alone tells you something about how they work.

PEOs typically charge in one of two ways: a flat fee per employee per month, often shortened to PEPM, or a percentage of your total payroll. The administrative fee covers the PEO’s services. Benefits premiums and the payroll taxes themselves are billed on top of that fee. Workers’ comp premiums may be too, or they may be bundled into the fee, depending on the provider.

ASOs almost always charge a flat per-employee-per-month fee, sometimes with a base monthly charge. Because you keep your own benefit plans and workers’ comp, those costs stay with your existing carriers and brokers.

HRO pricing is scoped to the function you are handing over. It is usually a monthly retainer or a per-employee charge tied to the services included, and it does not move with your payroll. Because recruiting is inside the scope, you are not paying a separate placement fee every time you hire.

Percent-of-payroll pricing deserves one caution. As you give raises and add higher-paid staff, the fee rises with your payroll even if the vendor’s work does not change. Flat pricing does not have that effect. Over three years of growth, that difference compounds.

For the published price bands, the sources behind them, and a worked example for a 20-person company, see How much does a PEO cost?

How to decide: five questions

Answer these five and you will get a recommendation. Two answers rule HRO out, and they should: if you want to hand off the employer-of-record role, or you need a PEO’s benefits pool, a PEO is the right call. Everything else points to HRO.

Whatever you choose, ask for the contract in writing, ask who is liable for what, and check the IRS list if anyone uses the word “certified.”