Tax ID Number

What does tax ID number mean in U.S. federal tax usage?

On a U.S. federal tax document, “tax ID number” can refer to any of the five identifiers in the IRS TIN taxonomy. The Social Security Administration issues Social Security numbers (SSNs). The IRS issues employer identification numbers (EINs), individual taxpayer identification numbers (ITINs), adoption taxpayer identification numbers (ATINs), and preparer taxpayer identification numbers (PTINs).

The label alone does not tell you which number to enter. A federal TIN may be requested on a tax return, statement, other tax-related document, or certain withholding certificates. The right type depends on who or what the form identifies and why the number is needed. A state agency or foreign tax authority may use a different identifier and its own rules, outside the U.S. federal TIN classification.

How do the main U.S. tax ID numbers differ?

The five federal TINs differ by whom or what they identify and the federal tax role they serve.

SSN and ITIN: individual identifiers with different eligibility and limits

SSN. For most individuals, the federal TIN is a Social Security number.

ITIN. An individual taxpayer identification number is for someone who needs a U.S. TIN for a federal tax purpose but is not eligible for an SSN.

ITIN limits and renewal check

An ITIN is for federal tax purposes only. It does not authorize employment in the United States, provide or change immigration status, qualify its holder for Social Security benefits, or serve as identification outside the federal tax system.

Check why an older ITIN is being used before assuming it needs renewal. An ITIN expires on December 31 of the third consecutive tax year in which it has not been used on a federal income-tax return. The holder must renew it when they need to file a federal tax return. However, the IRS requester instructions for Form W-9 allow an expired ITIN to be used on Form W-9. That exception does not remove the renewal requirement when the holder needs to file a federal return.

EIN: an identifier for businesses and other entities

An employer identification number is a federal tax ID for businesses, tax-exempt organizations, and other entities. The IRS criteria include having employees, owing specified business taxes, withholding certain tax on payments to a nonresident alien, or operating particular entity types. An EIN is not automatic for every business or single-member LLC, so an entity should check the current IRS criteria for its situation.

An EIN application generally identifies a responsible party: the person who controls the entity and its assets. This is an IRS application role; it does not automatically mean a beneficial owner, company officer, payroll contact, or formation service. The IRS states that nominees are not authorized to apply for an EIN.

ATIN and PTIN: identifiers for specific roles or situations

ATIN. An adoption taxpayer identification number is a temporary nine-digit IRS number for a child in a pending U.S. adoption when the adopting taxpayer cannot obtain the child’s SSN in time to file a tax return. It is limited to a child who is a U.S. citizen or resident. It is not a general child TIN or a permanent substitute for an SSN.

PTIN. A preparer taxpayer identification number identifies a paid tax return preparer. Someone compensated for preparing, or assisting with preparing, all or substantially all of a U.S. federal tax return or refund claim generally needs a current PTIN, subject to IRS-listed exceptions. A PTIN identifies the preparer in that role, rather than the taxpayer or the preparer’s business entity.

How do you identify the number a request actually needs?

First establish the authority and jurisdiction behind the request. Then match the identifier to the taxpayer’s status and the stated tax or reporting purpose.

Check the requesting authority and jurisdiction first

An EIN is a federal tax ID, while a state tax ID belongs to a separate state system. Requirements and registration steps vary. The SBA overview of federal and state tax ID numbers distinguishes the two systems and directs businesses to state government websites for local rules. Check the applicable state authority instead of assuming an EIN answers a state request. This does not mean every business needs a state tax ID or that a state can never ask for an EIN; the agency and its request control.

The same care applies to a request for a foreign tax identifier. In specified U.S. withholding and reporting contexts, for example, Form W-8BEN instructions address a nonresident alien individual’s foreign status, beneficial-owner capacity, and possible treaty benefits. The form can request a U.S. SSN or ITIN if required and a foreign TIN from the person’s jurisdiction of tax residence. A foreign entity generally uses Form W-8BEN-E instead. Neither possession of a U.S. TIN nor possession of a foreign TIN determines the right form or field by itself. The person type, transaction, and form instructions matter.

Read the exact request before sharing a number

Before entering a number, identify:

• the exact form or identifier named;
• whose status or activity the form documents;
• the requesting authority and jurisdiction; and
• the stated tax or reporting purpose.

These questions help interpret a request, but they do not resolve every withholding or entity-classification issue. Form W-9, for example, gives a requester a U.S. person’s correct TIN for federal information reporting. The current form generally calls for an individual’s SSN and other entities’ EINs, with special instructions for resident aliens, sole proprietors, and disregarded entities. For detailed completion guidance, see 4dev’s Form W-9 guide.

A request for a TIN or Form W-9 does not by itself establish that Form 1099-NEC must be filed. Form 1099-NEC has a separate reporting workflow for nonemployee compensation; see 4dev’s Form 1099-NEC guide for that topic.

Locate or confirm an existing number through the issuing authority

Use the issuing authority’s records instead of applying for a replacement identifier simply because the number is missing. For an EIN, the IRS lists confirmation routes that include an entity transcript, a downloadable CP575 verification notice for eligible Business Tax Account users, and Letter 147C requested through the IRS business tax line. The IRS EIN guidance also lists records where an existing EIN may appear, such as the original IRS notice, prior business returns, or certain institutional records. Access depends on the person’s authority to receive the number.

SSNs and ITINs have different recovery paths. The SSA provides a replacement Social Security card process, although a physical card is often unnecessary when the number is known. The IRS issues an ITIN assignment notice called CP565; a holder who cannot find it should contact the IRS. These routes are for the number holder, not for a payer, employer, or other third party seeking someone else’s identifier.

What should you do before sharing a tax ID number?

Treat a tax ID as sensitive information. IRS identity-protection guidance identifies SSNs and EINs as personally identifiable information. Confirm who is asking, why the number is needed, and which transmission method the legitimate requester specifies. Avoid publishing or casually sending the number. Ordinary email is not encrypted, so use the secure portal or encrypted workflow provided for the transaction when one is available.

Keep a tax ID separate from an IRS IP PIN

An IRS Identity Protection PIN (IP PIN) is a six-digit authentication number used to validate the owner of an SSN or ITIN on specified federal individual income-tax returns. The IRS generates a new IP PIN each year. It is not a taxpayer identification number and does not replace an SSN or ITIN.

Do not enter an IP PIN in a TIN field or share it outside the return-preparation situations the IRS describes. If a form asks for a tax ID, provide the requested TIN only after confirming that the form and requester call for it. An IP PIN has a separate authentication role.