Is an EIN the same as a Social Security Number?

No. A Social Security Number identifies an individual, while an Employer Identification Number identifies a business or employer for federal tax purposes. Both are nine digits, but they serve different roles. Payroll filings and W-2 forms use the employer's EIN, not the owner's Social Security Number.

Does my employee's W-2 show my EIN or the PEO's?

If you employ through a PEO, the W-2 usually shows the PEO's EIN, because the PEO files the payroll taxes under its own number. This is normal in co-employment. It is one reason to confirm the PEO is IRS-certified, which affects tax liability and certain credits.

Do I need an EIN to hire someone outside the United States?

An EIN is a US tax identifier, so it applies to hiring within the United States. In another country, the equivalent is registering with that country's tax authority, or employing through an Employer of Record that already holds the local registrations in place of a US-style EIN.

Glossary

Employer Identification Number

An Employer Identification Number (EIN) is the nine-digit tax identifier the US Internal Revenue Service issues to an employer for filing payroll taxes and wage statements, and in a PEO arrangement the PEO files under its own EIN rather than the client's.

Reviewed by Teamed's in-house employment-law team·Last updated 28 July 2026

Also known as: federal employer identification number, FEIN

What is Employer Identification Number?

An Employer Identification Number (EIN) is a nine-digit number issued by the United States Internal Revenue Service to identify a business for tax purposes. An employer uses its EIN to file payroll taxes, report wages, and appear on the W-2 forms its employees receive at year end. It is applied for using IRS Form SS-4.

The EIN becomes important in co-employment. When a business uses a Professional Employer Organisation, the PEO pays the workers and files their payroll taxes under its own EIN, not the client's. So the employees' W-2 forms show the PEO's number, even though they do the client's work day to day.

This is why the certification status of a PEO matters. Because the wages run under the PEO's EIN, a client should check that the PEO is IRS-certified, which affects who is liable for the employment taxes and whether certain federal tax credits are preserved. The EIN on the filing signals who the tax system treats as the employer.

Whose EIN appears on a worksite employee's W-2?

In a PEO arrangement, the PEO's. Because the PEO pays wages and files employment taxes under its own Employer Identification Number, the W-2 forms the workers receive show the PEO as the filing employer, not the client company, even though the workers do the client's day-to-day work.

How do you get an EIN?

A business applies to the Internal Revenue Service using Form SS-4, and can do so online, by fax or by post. The IRS then issues a unique nine-digit number in the format NN-NNNNNNN. The number stays with the business and is used on all its federal payroll and tax filings.

Why does the PEO's EIN matter to a client?

Because the workers' wages and taxes run under it, the client should confirm the PEO is an IRS-certified PEO. Certification affects who carries the federal employment-tax liability and whether the client keeps certain payroll tax credits. The EIN on the filing marks who the tax authority treats as the employer.

Key facts

EIN format and application: An EIN is a nine-digit number in the format NN-NNNNNNN, issued by the US Internal Revenue Service and applied for using Form SS-4; it identifies the employer on all federal payroll tax filings and employee W-2 forms.Source: Internal Revenue Service· verified 2026-07-28
Certified PEO files under its own EIN: Under Internal Revenue Code sections 3511 and 7705, a Certified PEO is treated as the sole employer of worksite employees for federal employment taxes on the wages it pays, filed under the CPEO's own EIN rather than the client's.Source: Internal Revenue Service· verified 2026-07-28

Frequently asked questions

Is an EIN the same as a Social Security Number?
No. A Social Security Number identifies an individual, while an Employer Identification Number identifies a business or employer for federal tax purposes. Both are nine digits, but they serve different roles. Payroll filings and W-2 forms use the employer's EIN, not the owner's Social Security Number.
Does my employee's W-2 show my EIN or the PEO's?
If you employ through a PEO, the W-2 usually shows the PEO's EIN, because the PEO files the payroll taxes under its own number. This is normal in co-employment. It is one reason to confirm the PEO is IRS-certified, which affects tax liability and certain credits.
Do I need an EIN to hire someone outside the United States?
An EIN is a US tax identifier, so it applies to hiring within the United States. In another country, the equivalent is registering with that country's tax authority, or employing through an Employer of Record that already holds the local registrations in place of a US-style EIN.

Related terms

Note

This is general information, not legal advice. Statutory rules vary by country and change over time.

Glossary

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Last verified 2026-07-28