Employment outsourcing covers several different products that get sold under one phrase: payroll processing, payroll tax agency, co-employment through a PEO, and full legal employment through an employer of record. They differ on the question that matters most when something goes wrong, which party is liable for employment taxes and employer obligations. The IRS is explicit that the answer depends on the arrangement type: a client can remain solely liable, become jointly liable, or in the certified PEO case be relieved of liability. This page maps the models to that liability ladder so you can name the one you are actually buying.
The delegation ladder: from payroll processing to co-employment
At the light end, a payroll service provider calculates pay and files returns while you remain the employer of record for everything; the IRS warns that if such a provider defaults, the employer remains responsible for depositing the taxes and filing on time. Reporting agents and Section 3504 agents take on more of the filing mechanics, with liability shared in defined ways. A PEO goes further: under co-employment it becomes the administrative employer, running payroll, benefits and HR compliance for your existing workforce, while you keep direction of the work. NAPEO, the industry body, describes the product as payroll, benefits, compliance assistance and other HR services delivered through that shared model.
Where liability actually moves: the CPEO case
The IRS's general position on third-party payers is that employers are ultimately responsible for income tax withheld and both portions of social security and Medicare taxes. The exception it names is certification: in certain situations, employers who are customers of a certified professional employer organization are relieved of their liability for income tax withholding and social security and Medicare taxes. Certification is granted by the IRS under a program established by the Tax Increase Prevention Act of 2014, requires a demonstrated history of financial responsibility and tax compliance, and the list of certified organisations is public. If tax liability relief is the reason you are outsourcing, the CPEO register is the filter that matters.
The full transfer: employer of record
An employer of record is the far end of the ladder: it is the sole legal employer, used where you have no entity at all, most often for hiring abroad. The EOR signs the local employment contract, runs payroll and statutory filings in the employee's country, and carries the legal employer obligations under that country's labour law; you direct the day-to-day work and pay salary plus a fee. The distinction from a PEO is structural, not cosmetic: a PEO co-employs staff your own entity already employs, while an EOR employs where you cannot. Several vendors in this index sell both models, at different prices, and the verified pricing table shows the fee shapes side by side.
Choosing a model deliberately
Pick by naming what you want to transfer. If it is administrative load only, a payroll provider or ASO-style arrangement is cheapest and leaves liability with you. If it is benefits scale and HR compliance for a domestic team, a PEO fits, and IRS certification determines the tax liability position. If it is legal employment in a country where you have no entity, only an EOR does that job. Write the chosen model into the contract explicitly, including whose EIN or local registration the filings run under, because that detail, not the marketing label, is what decides liability when a filing is missed. Nothing here is legal or tax advice; the agreements and the tax authority's rules control.
Questions people ask about employment outsourcing
Does outsourcing payroll remove my tax liability?
Usually not. The IRS states that employers generally remain ultimately responsible for withheld income tax and social security and Medicare taxes, and that in a provider default the employer must still deposit and file. The named exception is the certified PEO arrangement, where customers are relieved of liability in certain situations.
What is the difference between employment outsourcing through a PEO and an EOR?
A PEO co-employs a workforce your own entity already legally employs, handling payroll, benefits and compliance. An EOR is the sole legal employer, used where you have no entity, typically for hires in other countries.
What should the contract state about tax filings?
Which party files, under whose identification number, and who is liable if a deposit or return is missed. The IRS's third-party payer guidance turns on exactly these mechanics, so they belong in the agreement rather than in assumptions.