A tax ID is the identifying number the IRS uses to track your income, payments, and filings, formally called a Taxpayer Identification Number (TIN). Federal law requires one on nearly every tax return, payroll record, and bank account application in the country.1Office of the Law Revision Counsel. 26 U.S.C. 6109 – Identifying Numbers Which one you need depends on who you are and what you’re doing: individuals, businesses, foreign filers, adoptive parents, and paid tax preparers each use a different type.
The Five Types of Tax IDs
The IRS recognizes five kinds of TINs:
- Social Security Number (SSN). The default identifier for U.S. citizens and eligible residents, issued by the Social Security Administration.
- Employer Identification Number (EIN). A nine-digit number for businesses, nonprofits, trusts, and estates. It works like a Social Security number for an organization.2Internal Revenue Service. Employer Identification Number
- Individual Taxpayer Identification Number (ITIN). A nine-digit number for people who must file a U.S. return but aren’t eligible for an SSN, including certain nonresident aliens and their dependents.3Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
- Adoption Taxpayer Identification Number (ATIN). A temporary number that lets adoptive parents claim a child as a dependent while a domestic adoption is still being finalized.4Internal Revenue Service. Adoption Taxpayer Identification Number
- Preparer Tax Identification Number (PTIN). Required for anyone who prepares federal tax returns for pay. The application fee is $18.75 for 2026.5Internal Revenue Service. PTIN Requirements for Tax Return Preparers6Internal Revenue Service. PTIN Top FAQ 4
Which Tax ID You Need
Individuals
Every person earning income in the United States needs a valid tax ID to file. U.S. citizens and permanent residents use their SSN. Foreign nationals who have a federal filing requirement but can’t get an SSN use an ITIN instead.7eCFR. 26 CFR 301.6109-1 – Identifying Numbers
Businesses
Partnerships, corporations, LLCs, and nonprofits all need their own EIN.2Internal Revenue Service. Employer Identification Number A sole proprietor can generally use a personal SSN, but an EIN becomes necessary once the business hires employees, files excise tax returns, or sets up a retirement plan.8Internal Revenue Service. Understanding Your EIN Many sole proprietors get one anyway to avoid handing out their SSN to clients and vendors.
Trusts and Estates
A revocable living trust typically uses the grantor’s SSN while the grantor is alive. Once the grantor dies and the trust becomes irrevocable, the successor trustee must obtain an EIN because the trust is now a separate taxpaying entity. A decedent’s estate also needs its own EIN to file estate income tax returns.
Banks and Financial Accounts
Federal banking regulations require financial institutions to collect a tax ID when you open an account, personal or business. Banks use your TIN to report interest on Form 1099-INT and to comply with anti-money laundering rules that require verifying the identity of account holders and beneficial owners.9FinCEN.gov. CDD Rule FAQs
How to Get an SSN
Most Americans receive an SSN at birth through hospital birth registration. If you need one later, as an adult citizen or as a noncitizen authorized to work, you apply through the Social Security Administration using Form SS-5. The SSA requires original documents proving citizenship or immigration status, age, and identity. Common examples include a U.S. birth certificate, U.S. passport, Certificate of Naturalization, or current DHS immigration document.10Social Security Administration. Learn What Documents You Will Need to Get a Social Security Card Anyone age 12 or older applying for the first time must appear in person at a Social Security office.
How to Get an EIN
The fastest route is the IRS online application at irs.gov, which issues your EIN on screen once approved.11Internal Revenue Service. Get an Employer Identification Number You can also file Form SS-4 by fax (about four business days) or by mail (roughly four weeks).2Internal Revenue Service. Employer Identification Number
The application asks for the legal name of the entity, the entity type, and the reason for applying. You must also name a “responsible party,” meaning the individual who owns or controls the entity’s funds, and provide that person’s SSN or ITIN. The responsible party has to be a person, not another entity: usually the principal officer of a corporation, the general partner of a partnership, or the grantor or trustee of a trust.12Internal Revenue Service. Responsible Parties and Nominees There is no fee. If you lose yours, call the IRS Business and Specialty Tax Line at 800-829-4933 or check the CP 575 confirmation notice the IRS mailed when your number was issued.
How to Get an ITIN
ITIN applications use Form W-7, which you submit with a federal tax return unless you qualify for an exception. A valid passport is the simplest supporting document because it proves both identity and foreign status on its own. Without a passport, you need at least two other documents from the IRS’s approved list, such as a birth certificate, national identification card, or foreign driver’s license.13Internal Revenue Service. Instructions for Form W-7
You can apply three ways:
- By mail to the IRS ITIN Operation, P.O. Box 149342, Austin, TX 78714-9342.14Internal Revenue Service. How to Apply for an ITIN
- In person at a designated IRS Taxpayer Assistance Center.
- Through a Certifying Acceptance Agent, an IRS-authorized professional who verifies your documents so you don’t have to mail originals.
Processing normally takes 7 to 11 weeks and runs longer during peak filing season from January through April.
Keeping an ITIN Active
An ITIN doesn’t last forever. If you don’t use yours on a federal return for three consecutive years, it expires on December 31 of that third year.15Internal Revenue Service. How to Renew an ITIN Filing with an expired ITIN delays processing, holds up refunds tied to credits like the Child Tax Credit, and can trigger penalties and interest.
Renewal means submitting a new Form W-7 with identity documents. You don’t need to attach a tax return this time. One limit worth knowing: if your ITIN only appears on information returns like a Form 1099 and you aren’t filing your own return, you don’t need to renew. The expired ITIN still works for third-party reporting.
Penalties and Protecting Your Number
Omitting a tax ID from a document that requires one carries a $50 penalty per failure, capped at $100,000 per calendar year.16Office of the Law Revision Counsel. 26 U.S.C. 6723 – Failure to Comply With Other Information Reporting Requirements A missing or incorrect number on a Form W-9 can also trigger backup withholding at 24% on payments you receive, meaning the payer holds back nearly a quarter of the money until the problem is fixed.
A stolen SSN or ITIN can be used to file a fraudulent return in your name and claim your refund. The IRS offers a free Identity Protection PIN, a six-digit number that blocks anyone from filing under your SSN or ITIN without it.17Internal Revenue Service. Get an Identity Protection PIN Anyone with an SSN or ITIN can enroll, most easily through an IRS online account. The PIN changes each year, and you retrieve the new one through your online account every January.18Internal Revenue Service. FAQs About the Identity Protection Personal Identification Number (IP PIN)