US Tax IQ: Types of Tax ID Numbers and How to Get One

The United States uses five types of tax identification numbers, and the one you need depends on who you are and why you’re interacting with the tax system. US citizens and work-authorized residents use a Social Security Number (SSN). Foreign nationals with a US tax filing obligation but no SSN eligibility use an Individual Taxpayer Identification Number (ITIN). Businesses, partnerships, trusts, and estates use an Employer Identification Number (EIN). Paid tax preparers must hold a Preparer Tax Identification Number (PTIN). And prospective adoptive parents whose child doesn’t yet have an SSN can request a temporary Adoption Taxpayer Identification Number (ATIN). Each has its own issuing agency, application form, and documentation rules, so the first step is always identifying which category fits your situation.

Which Tax ID Number You Need

Every TIN is a nine-digit number the IRS uses to track tax obligations, but they’re not interchangeable. Match your situation to the right one before you file any paperwork.

How to Get a Social Security Number

SSNs are issued by the Social Security Administration, not the IRS. Most US citizens get one at birth, when parents apply at the hospital. If you never received one, or you’re a noncitizen who’s just been authorized to work, you’ll apply directly with the SSA.

Documents You’ll Need

The SSA accepts only originals or certified copies from the issuing agency. Photocopies and notarized copies are rejected. You need to prove three things: identity, age, and citizenship or immigration status.6Social Security Administration. Learn What Documents You Will Need to Get a Social Security Card

  • Citizenship: US passport, Certificate of Naturalization, or Certificate of Citizenship.
  • Age: US birth certificate, or a foreign birth certificate; the SSA may also accept a passport or DHS document.
  • Identity: current US driver’s license, state ID card, or US passport. If none of those are available, an employee ID card, school ID, or health insurance card may work.
  • Immigration status (noncitizens): Permanent Resident Card (Form I-551), Employment Authorization Document (Form I-766), or Form I-94 with an unexpired foreign passport. F-1 and M-1 students should also bring Form I-20; J-1 and J-2 exchange visitors need Form DS-2019.

How to Apply

Start the application at ssa.gov, then visit a local Social Security office to present your documents in person. After approval, your card arrives by mail in 5 to 10 business days.7Social Security Administration. Request Social Security Number for the First Time

How to Get an Employer Identification Number

Any entity that hires employees, operates as a corporation or partnership, or manages a trust or estate needs an EIN. Sole proprietors without employees can use their SSN instead, but many still get an EIN to keep their personal number off business paperwork. Applying is always free.

Applying Online

The IRS online application is the fastest route and issues your EIN immediately on the confirmation screen. To use it, the responsible party (the person who controls or directs the entity) must have a valid SSN, ITIN, or existing EIN, and the business must be located in the US or a US territory.3Internal Revenue Service. Get an Employer Identification Number

Have this information ready before you start, since the session times out after 15 minutes of inactivity: the business’s legal name and address, entity type (LLC, corporation, and so on), reason for applying, and the date the business started or acquired its assets. Each responsible party is limited to one EIN per day.

After you finish, the IRS mails a formal confirmation notice, CP 575, to the business address. The IRS issues that notice only once and cannot generate a duplicate, so file it with your formation documents.8Internal Revenue Service. Sample EIN Confirmation Letter

If You Don’t Have an SSN or ITIN

Foreign persons starting a US business often don’t have an SSN, ITIN, or existing EIN, and can’t use the online system. Three alternatives are available.9Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025)

  • Phone: international applicants can call 267-941-1099 (not toll-free), Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern, and receive an EIN during the call. Fill out Form SS-4 before you dial.
  • Fax: complete Form SS-4 and fax it to the IRS. You’ll get your EIN back by fax within about four business days.
  • Mail: the slowest route. The IRS recommends mailing Form SS-4 four to five weeks before you need the number.

The responsible party’s name and title on Form SS-4 must match the entity’s formation documents exactly. Any discrepancy triggers a manual review and delays processing.

Recovering a Lost EIN

If you can’t find your CP 575, check bank records, past business tax returns, or state and local license applications where the number was used. If none of those turn it up, call the IRS Business and Specialty Tax Line at 800-829-4933 (Monday through Friday, 7:00 a.m. to 7:00 p.m. local time). After verifying your identity, the IRS can give the EIN over the phone.10Internal Revenue Service. Employer Identification Number

How to Get an Individual Taxpayer Identification Number

An ITIN is for people who must file a US federal tax return but aren’t eligible for an SSN. That covers nonresident aliens with US-source income, resident aliens who don’t qualify for an SSN, and their spouses or dependents. If you later become eligible for an SSN, you must switch to it and stop using the ITIN.2Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)

The application is Form W-7, and its documentation rules are stricter than for other TINs. This is where most applicants stumble.

Documents You’ll Need

You must prove both your identity and your foreign status. The IRS accepts 13 specific document types, and every submitted document must be an original or a certified copy from the issuing agency. Notarized copies are not accepted.11Internal Revenue Service. Instructions for Form W-7 (12/2024) – Section: Supporting Documentation Requirements

A valid passport is the only single document that proves both identity and foreign status. Without one, you need at least two documents: for example, a national ID card (showing name, photo, address, date of birth, and expiration date) paired with a civil birth certificate, or a foreign driver’s license with a US visa. At least one document must include a photograph, unless the applicant is a dependent under 14.

Mailing original passports and national IDs to the IRS makes many applicants uneasy. The main alternative is a Certifying Acceptance Agent (CAA), an individual or firm authorized by the IRS to verify your documents in person and submit certified copies for you. The IRS maintains a directory of approved CAAs by state and country.12Internal Revenue Service. ITIN Acceptance Agents CAAs charge a professional fee, typically $150 to $300.

Submitting the Application

Your completed Form W-7 must generally be attached to a valid US federal income tax return (Form 1040, 1040-NR, or 1040-SR). The IRS won’t process a standalone W-7 unless you qualify for one of five specific exceptions covering situations where you need a TIN but aren’t required to file a return, such as receiving passive income subject to third-party withholding, claiming a tax treaty benefit on wages or scholarships, having a US mortgage that requires TIN reporting, being party to a sale of US real property by a foreign person, or acting as a non-US representative of a foreign corporation with e-filing obligations. If you qualify for an exception, check the corresponding box on Form W-7 and attach the required supporting documents in place of a return. Missing that box is one of the fastest ways to get rejected.13Internal Revenue Service. Instructions for Form W-7 (12/2024) – Section: Applying for an ITIN for the First Time

Three submission routes are available:

  • Mail Form W-7, your tax return (if required), and your original or certified documents to the IRS ITIN Operation in Austin, Texas. This is the slowest option and the riskiest for your documents.
  • Use a Certifying Acceptance Agent, who verifies documents in person and submits the package with a Certificate of Accuracy.
  • Schedule an appointment at a designated IRS Taxpayer Assistance Center. Staff review your originals and Form W-7 in person, then forward the application to Austin.

Standard processing takes about seven weeks. From January 15 through April 30, or for applications sent from overseas, expect nine to eleven weeks.14Internal Revenue Service. How to Apply for an ITIN – Section: After You Apply An incomplete package will trigger a letter requesting resubmission and add significant time.

Renewing an ITIN

An ITIN expires on December 31 after three consecutive tax years of non-use. If it’s not included on a federal return for three years running, it goes inactive.15Internal Revenue Service. How to Renew an ITIN

The IRS has also expired older ITINs by middle digits. ITINs with middle digits 70 through 88 and 90 through 99 (all issued before 2013) have expired and must be renewed before use on a return. Renewal requires a fresh Form W-7 with new identity and foreign status documentation, but you don’t need to attach a tax return unless the ITIN also expired from non-use. Start early; last-minute renewals almost always delay refunds.

Adoption Taxpayer Identification Number

An ATIN is a temporary TIN for a child placed with prospective adoptive parents by an authorized agency when the adoption isn’t yet final. Because the adoption is pending, the SSA often won’t issue an SSN for the child, which would otherwise leave the adoptive parents unable to claim the dependent.5eCFR. IRS Adoption Taxpayer Identification Numbers

To qualify, the prospective adoptive parent must be eligible to claim the child as a dependent, the placement must come from an authorized agency, and the parent must have tried and failed to get an SSN for the child. Apply using Form W-7A with proof of the child’s identity and US residency (such as a birth certificate, passport, or adoption decree).16Internal Revenue Service. Instructions for Form W-7A, Application for Adoption Taxpayer Identification Number Once the adoption is finalized and the child gets an SSN, stop using the ATIN and switch to the SSN on future returns.

Preparer Tax Identification Number

Anyone paid to prepare or help prepare federal tax returns must have a current PTIN before working on a client’s return. That applies to enrolled agents, CPAs acting as preparers, and uncredentialed preparers alike.4Internal Revenue Service. PTIN Requirements for Tax Return Preparers

Most first-time applicants can get a PTIN in about 15 minutes through the IRS Return Preparer Office system at rpr.irs.gov. The fee is $18.75 and non-refundable.17Internal Revenue Service. IRS Reminds Tax Pros to Renew PTINs for the 2026 Tax Season Every PTIN expires December 31, so preparers renew each fall. The renewal window typically opens in mid-October, and the renewal fee is the same $18.75.18Internal Revenue Service. Frequently Asked Questions: PTIN Application/Renewal Assistance

Protecting Your Tax ID Number

Your TIN is the key to your tax identity, and a stolen one lets someone file a fraudulent return in your name. Provide your SSN, ITIN, or EIN only when it’s legally required, typically to employers, financial institutions, and government agencies. When a business or contractor needs it, the standard channel is Form W-9.19Internal Revenue Service. About Form W-9, Request for Taxpayer Identification Number and Certification The IRS initiates contact by physical mail, not email, phone, or text, so treat any unsolicited request through those channels as a scam.

If you’re worried about tax identity theft, the IRS runs an Identity Protection PIN program. An IP PIN is a six-digit number known only to you and the IRS; a return filed under your number without it will be rejected. Anyone with an SSN or ITIN can request one through their IRS online account, including on behalf of dependents. A new IP PIN is generated each year, so retrieve the updated number every January.20Internal Revenue Service. Get an Identity Protection PIN

Keep your records current, too. Individuals report a name change by checking the name change box on their next Form 1040. For address changes, individuals file Form 8822; businesses and other entities file Form 8822-B, which also handles changes to the responsible party on an EIN.21Internal Revenue Service. About Form 8822, Change of Address

Finally, watch for name-TIN mismatches at your payers. Banks, brokerages, and other payers of reportable income often use the IRS TIN Matching program to check that your name and TIN line up with IRS records. If they don’t (say, your bank has a maiden name and your SSN is under your married name), the payer may be required to start backup withholding at 24% on your payments until you fix it.22Office of the Law Revision Counsel. 26 US Code 3406 – Backup Withholding Make sure every payer has the exact name on file that matches your TIN at the IRS.