A Taxpayer Identification Number, or TIN, is a nine-digit number the Internal Revenue Service uses to identify every person and entity that files a return, earns reportable income, or otherwise shows up in the federal tax system. Five different kinds exist, and which one you need depends on who you are and why the IRS needs to track you. Every TIN except the preparer version is free to obtain directly from the issuing agency.1Internal Revenue Service. Taxpayer Identification Numbers (TIN)
Federal law requires every person filing a return, and every person listed on someone else’s return, to have an identifying number.2Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers That’s the reason these numbers exist and the reason you can’t opt out of having one if you’re in the tax system at all.
The Five Types of TINs
Each TIN answers a different question about who the taxpayer is.
Social Security Number
The SSN is the identifier most people use. U.S. citizens qualify, and certain noncitizens with work authorization or a valid nonwork reason can also get one. It stays with you for life and doubles as your identifier for Social Security benefits.3Social Security Administration. Request a Social Security Number for the First Time
Employer Identification Number
An EIN is the business counterpart to an SSN. Partnerships, corporations, LLCs, trusts, estates, and tax-exempt organizations use one to file returns, open business bank accounts, and hire employees.4Internal Revenue Service. Employer Identification Number
Individual Taxpayer Identification Number
An ITIN is for people who have to file a federal return but can’t get an SSN. That covers nonresident aliens filing U.S. returns, resident aliens without work authorization, and dependents or spouses of U.S. citizens who lack an SSN. An ITIN does not authorize work in the United States and does not make you eligible for Social Security benefits.5Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
Adoption Taxpayer Identification Number
An ATIN is a temporary number for a child whose adoption is pending, so adoptive parents can claim the child as a dependent before an SSN is assigned. The IRS deactivates an ATIN two years after issuance if no SSN has been provided, though an extension is available if the adoption is still not final.6Internal Revenue Service. Adoption Taxpayer Identification Number
Preparer Taxpayer Identification Number
A PTIN is required for anyone who prepares or helps prepare federal tax returns for pay. It’s eight digits with a leading “P.” Unlike the others, it carries a fee: $18.75 per year for a new application or a renewal.7Internal Revenue Service. PTIN Requirements for Tax Return Preparers
When You Actually Need a TIN
Filing a federal income tax return is the obvious trigger. Plenty of ordinary financial activities pull one in too.
Banks and brokerages collect your number when you open an account so they can report interest and dividend income to the IRS and satisfy customer identification rules under the USA PATRIOT Act.8Financial Crimes Enforcement Network. FinCEN Permits Banks to Use Alternative Collection Method for Obtaining TIN Information Employers collect your SSN on your first day to report wages and withhold payroll taxes.9Social Security Administration. Employer W-2 Filing Instructions and Information
Claiming a dependent requires that person’s TIN. Without it, the IRS won’t allow the dependent claim, and you lose access to credits such as the Child Tax Credit.10Internal Revenue Service. Dependents Foreign nationals claiming reduced withholding under a tax treaty also need a TIN on their withholding certificate.11Internal Revenue Service. Claiming Tax Treaty Benefits
Estates have their own rule. If a deceased person’s estate produces more than $600 in annual gross income, the administrator has to get an EIN and file Form 1041.12Internal Revenue Service. File an Estate Tax Income Tax Return
How to Get Each One
Applying for an SSN
Most U.S. citizens get their SSN at birth through Enumeration at Birth, which uses the hospital’s birth registration data. If you didn’t get one that way, or you’re a noncitizen applying for the first time, you complete Form SS-5 and provide documents proving age, identity, and citizenship or immigration status. A U.S. birth certificate or passport handles citizenship. Noncitizens must present a current, unexpired Department of Homeland Security document such as Form I-551 or I-766.13Social Security Administration. Application for Social Security Card Form SS-5 You can start online, but you’ll need to visit a Social Security office to present original documents. There is no fee.3Social Security Administration. Request a Social Security Number for the First Time
Applying for an EIN
The IRS online EIN assistant is the fastest route. It issues the number immediately and costs nothing.14Internal Revenue Service. Get an Employer Identification Number You’ll provide the entity type, the reason for applying, and the name and SSN or ITIN of a responsible party. That responsible party has to be an individual, not another entity, unless you’re applying for a government organization.15Internal Revenue Service. Instructions for Form SS-4 (12/2025) You can also mail or fax Form SS-4, but processing takes longer. Third-party sites sometimes charge for this. According to the IRS, you never have to pay a fee for an EIN.
Applying for an ITIN
You file Form W-7, and in most cases you must attach the federal tax return the ITIN is being requested for. Along with the form and return, submit original identity documents or certified copies from the issuing agency. A passport is the only stand-alone document that proves both identity and foreign status; without one, you’ll need at least two other documents from the accepted list, and at least one must have a photograph.16Internal Revenue Service. Instructions for Form W-7 (12/2024)
If mailing original documents makes you uneasy, two alternatives exist. You can apply in person at an IRS Taxpayer Assistance Center, where staff verify your documents on the spot. Or you can use a Certifying Acceptance Agent, who is authorized by the IRS to authenticate your documents in person and return them immediately, then send only the application on.17Internal Revenue Service. ITIN Acceptance Agents
Mailed applications go to the IRS ITIN Operation center in Austin, Texas. Processing runs about seven weeks under normal conditions, and nine to eleven weeks during tax season (January 15 through April 30) or if you applied from overseas.18Internal Revenue Service. How to Apply for an ITIN
An ITIN doesn’t last forever. If yours isn’t used on a federal return for three consecutive years, it expires on December 31 of that third year, and filing with an expired ITIN can delay your refund. Renewing uses the same Form W-7 with the “Renew an existing ITIN” box checked and the same identity documentation.19Internal Revenue Service. How to Renew an ITIN
What Happens If You Don’t Provide a Correct TIN
Failing to give a payer a correct TIN triggers backup withholding: the bank, brokerage, or other payer must withhold 24% of your payments and send it to the IRS.20Office of the Law Revision Counsel. 26 USC 3406 – Backup Withholding You recover the money when you file your return, but you’re out the cash until then.
Businesses that file information returns like W-2s and 1099s face separate penalties for missing or incorrect TINs. For 2026:
- Corrected within 30 days: $60 per return
- Corrected after 30 days but by August 1: $130 per return
- Corrected after August 1 or never filed: $340 per return
- Intentional disregard: $680 per return, with no annual cap
These penalties apply separately to the filer copy and to the payee statement, so one botched 1099 can generate two penalties.21Internal Revenue Service. Information Return Penalties A small business issuing dozens of 1099s can accumulate a serious bill from a systemic error.
Keeping Your TIN Secure
A stolen SSN or ITIN can be used to file a fraudulent return in your name, often before you’ve filed yours. The IRS Identity Protection PIN program is the strongest preventive tool. Anyone with an SSN or ITIN can enroll through an IRS online account and receive a six-digit IP PIN. The IRS issues a new one each year, and any return filed without it is rejected.22Internal Revenue Service. Get an Identity Protection PIN
If you can’t verify your identity online and your adjusted gross income on your last filed return was under $84,000 ($168,000 for joint filers), you can submit Form 15227. The IRS then verifies your identity by phone and mails the IP PIN in four to six weeks. Parents and legal guardians can also request an IP PIN for their dependents.22Internal Revenue Service. Get an Identity Protection PIN
Business identity theft works differently. If you receive notice that an EIN was assigned to your business without your knowledge, first check whether a spouse, accountant, or bank requested it for a legitimate reason. If not, submit Form 14039-B, Business Identity Theft Affidavit, through your ID.me account online, or fax it to 855-807-5720.23Internal Revenue Service. If You Received an EIN You Didn’t Request