Learn About Finding Your Taxpayer Identification Number

What Is a Taxpayer Identification Number?

A Taxpayer Identification Number (TIN) is a nine-digit code that the Internal Revenue Service (IRS) uses to track your tax records. Think of it as your tax identity—much like a Social Security number serves as your personal identifier for government purposes. The TIN appears on tax forms, correspondence from the IRS, and any official tax documents you file or receive.

The most common type of TIN is the Social Security Number (SSN), which the Social Security Administration issues to U.S. citizens, permanent residents, and certain temporary residents. If you work in the United States, have ever filed a tax return, or receive benefits from Social Security or Medicare, you almost certainly have a Social Security Number that serves as your TIN.

However, the IRS recognizes several types of TINs beyond a Social Security Number. An Employer Identification Number (EIN) is used by businesses, corporations, partnerships, and nonprofit organizations. Individual Taxpayer Identification Numbers (ITINs) are issued to individuals who cannot obtain a Social Security Number but have a tax filing requirement or need to claim benefits. Adoption Taxpayer Identification Numbers (ATINs) are temporary numbers assigned to children awaiting adoption. Each serves a specific purpose within the tax system.

Understanding which type of TIN you need is important because the IRS requires this number on nearly every tax form and financial document. Banks ask for it when you open accounts, employers request it before you start work, and financial institutions need it to report interest earned or investment income. Your TIN is fundamental to how the federal government tracks your income, taxes paid, and eligibility for various programs.

Practical takeaway: Your TIN is the nine-digit code the IRS uses to identify you for tax purposes. Most people use their Social Security Number as their TIN, but other types exist for specific situations like business ownership or international workers.

Understanding Social Security Numbers as TINs

A Social Security Number (SSN) is the most widely used taxpayer identification number in the United States. The Social Security Administration (SSA) has issued more than 450 million Social Security Numbers since the program began in 1936. Your SSN follows a specific format: three digits, then two digits, then four digits (XXX-XX-XXXX). Each number is unique to one individual.

The Social Security Number was originally created to track earnings and benefits for the Social Security program, which provides retirement, disability, and survivor benefits. Over time, it became the standard identifier for many purposes beyond Social Security itself. Today, employers use SSNs to report your wages to the IRS. Banks and financial institutions use SSNs to report interest income and investment earnings. The IRS uses your SSN as your primary TIN when you file individual income tax returns.

If you are a U.S. citizen or permanent resident, you can obtain a Social Security Number from the Social Security Administration. Children born in the United States can receive an SSN at birth, though parents must request one. If you were not assigned a number at birth, you can apply for one at any age. Naturalized citizens and permanent residents can also receive Social Security Numbers through the SSA application process.

Your Social Security Number connects to your earnings record, which the Social Security Administration maintains. This record tracks how much you have earned throughout your working life and determines your eligibility for Social Security retirement, disability, and survivor benefits. Employers report your wages to the SSA using your SSN. The IRS also receives reports of your income from employers, banks, and other sources, all matched to your SSN.

Protecting your Social Security Number is critical because identity theft and fraud can occur when someone misuses your number. You should not share your SSN with businesses or organizations that do not have a legitimate reason to request it. When your SSN is requested, it is reasonable to ask why the organization needs it and how they will protect it.

Practical takeaway: Your Social Security Number is your primary TIN as an individual taxpayer. It tracks your earnings record for Social Security benefits and connects to your IRS tax records. Protect it carefully and only share it when there is a clear business reason.

Other Types of Taxpayer Identification Numbers

Beyond Social Security Numbers, the IRS issues other types of TINs for specific situations. Understanding which type of TIN you need depends on your individual circumstances and tax obligations.

An Employer Identification Number (EIN) is a nine-digit number assigned by the IRS to businesses, partnerships, corporations, nonprofit organizations, and other entities. The format is XX-XXXXXXX. If you own a business with employees, operate as a corporation or partnership, or run a nonprofit organization, you need an EIN. The IRS uses the EIN to track the business entity's tax returns, employment taxes, and other business tax information. Unlike a Social Security Number, which identifies a person, an EIN identifies a business entity. A single person may have both an SSN (their personal TIN) and an EIN (for their business). Sole proprietors without employees may or may not need an EIN, depending on their business structure and tax situation. The IRS provides a free EIN through their website or by telephone.

An Individual Taxpayer Identification Number (ITIN) is issued to individuals who have a U.S. tax filing requirement or need to claim certain credits but cannot obtain a Social Security Number. This includes some resident aliens, nonresident aliens, and dependents who are not eligible for SSNs. The ITIN follows the format XX-XX-XXXX, with the middle two digits falling between 50 and 92, which distinguishes it from a Social Security Number. The IRS issues ITINs through a special application process. Over 16 million ITINs have been issued since the IRS began the program in 1996. If you are in the United States without SSN eligibility but have earned income or need to file a tax return, an ITIN allows you to report your taxes correctly.

An Adoption Taxpayer Identification Number (ATIN) is a temporary nine-digit number used during the adoption process. It allows parents to claim an adopted child as a dependent on their tax return before the child receives a permanent Social Security Number. Once the adoption is finalized and the child receives an SSN, the ATIN is no longer used. The IRS issues ATINs specifically for this temporary purpose. Parents seeking to claim adoption tax credits or report an adopted child on their tax return typically need to request an ATIN.

Practical takeaway: Different situations require different TINs. Business owners need an EIN, certain foreign workers or dependents need an ITIN, and parents of children being adopted may need an ATIN. Identify which type applies to your situation.

How to Find Your Existing TIN

If you believe you already have a TIN but cannot remember it, several methods can help you locate it. Your TIN likely appears on important documents you have already received.

The easiest place to find your Social Security Number is on documents you already possess. Your SSN appears on your Social Security card, which the Social Security Administration mailed to you. If you keep important documents organized, your SSN is also printed on past tax returns you have filed, W-2 forms from employers, or 1099 forms from banks and other financial institutions. Many people also find their SSN on bank account statements, mortgage documents, or insurance policies. Check any official mail from the IRS, which typically lists your SSN on correspondence about your tax account.

If you have filed a tax return in past years, you can locate your SSN on copies of those returns. Tax returns filed with the IRS show your TIN prominently on the top of the form. If you no longer have printed copies, you may be able to order transcripts of past tax returns from the IRS. The IRS transcript service allows you to request a copy of your tax return or a record of account information. You can request transcripts online through the IRS website, by mail, or by phone. The IRS also provides a transcript tool that allows you to view and download recent tax returns electronically.

Your employer should also have a record of your Social Security Number. If you are currently employed, your pay stub lists your SSN. If you are not currently employed, you can contact previous employers to ask if they have your SSN on file. Your employer uses your SSN to report your wages on Form W-2.

If you have a Social Security card but cannot read the number clearly, you can