Taxpayer Identification Number (TIN)

A taxpayer identification number (TIN) is "an identification number used by the Internal Revenue Service (IRS) in the administration of tax laws", in the IRS's own words. Section 6109 of the Internal Revenue Code requires one, as the regulations prescribe, on returns and on the statements payers file about the people they pay. It is a category rather than a single number: the regulation lists SSNs, IRS individual taxpayer identification numbers, IRS adoption taxpayer identification numbers and employer identification numbers as the principal types, and paid return preparers use a fifth, the preparer tax identification number.

People often say "TIN" when they mean an EIN, because business forms ask for "taxpayer identification number" and businesses answer with their EIN. Both uses are correct: an EIN is one kind of TIN, and for an individual the TIN is usually their SSN.

Who uses which number. The regulation, 26 CFR 301.6109-1(a)(1)(ii), sets the defaults:

• An individual must use an SSN.
• An individual who is required to furnish a TIN but is not eligible for an SSN must use an individual taxpayer identification number.
• A corporation, partnership, trust, estate or other entity must use an employer identification number.
• An individual who is an employer, or who runs a business as a sole proprietor, should use an EIN where the form and its instructions call for it.

SSNs and ITINs look alike (nine digits, written 000-00-0000), and EINs are written 00-0000000. Every ITIN begins with 9.

Individual taxpayer identification numbers. The IRS issues an ITIN for federal tax purposes only, to certain nonresident and resident aliens, their spouses and their dependents who cannot get an SSN. An applicant files Form W-7, normally with the tax return that creates the need, plus documents proving identity and foreign status. The IRS says plainly what an ITIN does not do: it does not qualify anyone for Social Security benefits or the earned income credit, does not provide or change immigration status, does not authorize work in the United States and is not identification outside the federal tax system. Under section 6109(i)(3), an ITIN issued after 2012 expires if the holder does not file a federal return, and is not included as a dependent on someone else's, for three consecutive tax years; it then has to be renewed before it is used again.

Adoption and preparer numbers. An adoption taxpayer identification number (ATIN) is a temporary number for a child in the process of a legal adoption who is a U.S. citizen or resident but cannot get an SSN in time for the adoptive parents to file; it is requested on Form W-7A. A preparer tax identification number (PTIN) is required of anyone who prepares federal returns for pay, including every enrolled agent, and goes on the returns they prepare.

Why the number matters. Banks, brokers, employers and other payers report what they pay you to the IRS under your TIN, which is how the IRS matches information returns against your tax return. A payer who does not receive a correct TIN, usually on Form W-9, may be required to withhold at the backup withholding rate. Several tax benefits look for a particular type of number, not just any TIN: the earned income credit cannot be claimed with an ITIN, and for tax years beginning after 2025 the American opportunity credit requires a work-authorized SSN issued before the return's due date, for both the taxpayer and the student.

Protecting it. Because one number links income, refunds and credits, a stolen SSN or ITIN is the raw material of tax-related identity theft. The IRS offers an identity protection PIN, a six-digit code that must accompany any return filed under the number, to anyone who has an SSN or ITIN and can verify their identity.

1. Find the type that fits. A U.S. citizen or anyone authorized to work in the United States gets an SSN from the Social Security Administration. A person who has a federal tax need but cannot get an SSN applies for an ITIN on Form W-7. A business entity, estate or trust gets an EIN; so does a sole proprietor who has employees or meets one of the IRS's other EIN triggers.

2. Use it everywhere the IRS sees you. Your return, every Form W-2 and 1099 issued to you, Form W-9 when a payer asks, and any dependent's line on a return all carry a TIN.

3. Match it to the name. Information returns are matched by number and name, so a name change that has not reached the Social Security Administration, or a transposed digit, can produce a mismatch notice, a rejected e-file or backup withholding.

4. Keep it active. An ITIN that goes three consecutive years without being used on a federal return expires and must be renewed; an SSN does not expire.

For example: Amara has an SSN, and her husband Kofi, who is not eligible for one, has an ITIN. On their joint return each is identified by their own number. Their interest income of $1,800 is reported to the IRS under Amara's SSN, the number she gave the bank on Form W-9. If the bank had no valid TIN on file, it could have withheld 24 percent, or $432, of that interest as backup withholding.

Pros

• One number ties together every return, information return and payment, so income is matched to the right person and refunds go to the right place.
• The ITIN lets people who cannot get an SSN still file, pay tax, claim dependents and claim the benefits the law allows them.
• Separate business numbers (EINs) let sole proprietors keep their SSN off forms they hand to clients and vendors.

Cons

• Because the number unlocks refunds and credits, it is a target for identity theft, and a compromised number can take months to clear.
• An ITIN does not qualify for several credits that require an SSN, which families with mixed status often learn only when a credit is denied.
• A missing or mismatched TIN can trigger backup withholding or delays even when no tax is owed.