ITIN vs SSN for Filing Taxes Explained

Introduction

When we file taxes in the United States, the IRS needs a way to identify us — to match our tax return to our financial records and ensure our payments and filings are correctly recorded.

This identification happens through a tax identification number. Every individual who files a U.S. tax return is required to include one.

For most people who grew up in the United States, this number is something they have had since childhood and use without thinking about it. For immigrants navigating the U.S. system for the first time, it is often a source of genuine confusion — because there are two different numbers that can serve this purpose, issued by two different government agencies, for two different groups of people.

Those two numbers are the Social Security Number (SSN) and the Individual Taxpayer Identification Number (ITIN).

Understanding what each one is, who receives it, and how it is used when filing taxes removes a significant source of uncertainty — and helps us engage with the U.S. tax system correctly and confidently.

What a Social Security Number Is

A Social Security Number, or SSN, is a nine-digit identification number issued by the Social Security Administration (SSA) — a U.S. government agency separate from the IRS.

The SSN was originally created in the 1930s to track workers’ earnings and eligibility for Social Security retirement and disability benefits. Over time, its use expanded significantly. Today, the SSN serves as a primary identification number across many areas of American life.

An SSN is used for:

Employment. Employers in the United States are required to verify workers’ eligibility and report wages to the government. The SSN is the number used for this reporting. Without an SSN, most forms of authorized employment in the U.S. are not possible.

Social Security benefits. The SSN tracks an individual’s work history and contributions to the Social Security system — information that determines eligibility for retirement, disability, and survivor benefits later in life.

Tax reporting. The SSN is the primary number used to identify individuals when filing federal and state tax returns, and when employers report wages to the IRS through documents like the W-2.

Credit and financial services. The SSN is used by credit bureaus to build and maintain credit files, and by financial institutions when verifying identity. We discuss this in our guide How to Build Credit in the U.S. Without a Social Security Number.

Who receives an SSN? U.S. citizens are eligible for an SSN from birth. Permanent residents — those with green cards — are also eligible. Certain authorized temporary workers on specific visa categories may be eligible as well, depending on their work authorization status.

The key point is that the SSN is tied to work authorization and participation in the Social Security system. If someone is not authorized to work in the United States or is not eligible for Social Security benefits, they generally cannot obtain an SSN.

What an ITIN Is

An Individual Taxpayer Identification Number, or ITIN, is a nine-digit number issued by the Internal Revenue Service (IRS) — the federal agency responsible for tax collection and administration.

Unlike the SSN, the ITIN exists for one specific purpose: to allow individuals who have a U.S. tax filing obligation to comply with that obligation when they are not eligible to obtain an SSN.

The ITIN always begins with the number 9, which distinguishes it from an SSN. It is formatted the same way as an SSN — nine digits in three groups — but its origin and purpose are entirely different.

Who typically uses an ITIN? Common situations include:

Immigrants who are present in the United States and earn income here but are not eligible for an SSN based on their current immigration status. International students on F-1 or J-1 visas who have U.S. tax filing requirements. Nonresident aliens who earn certain types of U.S.-source income and must report it to the IRS. Dependents or spouses of U.S. citizens or resident aliens who need to be listed on a tax return but do not have SSNs of their own.

To obtain an ITIN, an individual submits IRS Form W-7 along with documentation verifying their identity and foreign status. This application can be submitted directly to the IRS, through an IRS-authorized Acceptance Agent, or through a certified tax professional who is authorized to certify identity documents.

ITINs may expire if they are not used on a federal tax return for a certain period of years, or based on IRS renewal schedules for certain ITIN series. It is worth verifying the current status of an ITIN through the IRS if it has not been used recently.

The Key Differences Between SSN and ITIN

Now that we understand each number individually, the differences between them become clear.

Issuing agency. An SSN is issued by the Social Security Administration. An ITIN is issued by the Internal Revenue Service. These are two separate government agencies with different functions — one manages retirement and employment programs, the other manages tax collection.

Who qualifies. An SSN is available to U.S. citizens, permanent residents, and certain authorized workers. An ITIN is available to individuals who have a U.S. tax obligation but do not qualify for an SSN — primarily non-citizens without current work authorization or Social Security eligibility.

Primary purpose. An SSN serves multiple purposes across employment, Social Security, credit, and taxes. An ITIN serves one primary purpose: tax identification. It exists specifically so that people who cannot get an SSN can still fulfill their tax obligations.

Work authorization. Holding an SSN — particularly one issued with work authorization — is connected to the right to work legally in the United States. An ITIN carries no work authorization whatsoever. Having an ITIN does not mean we are authorized to work in the United States, and it cannot be used to demonstrate work eligibility to an employer.

Social Security benefits. An SSN is the number through which Social Security contributions are tracked and benefits are earned. An ITIN is not connected to Social Security in any way. Taxes paid using an ITIN do not accumulate Social Security credits.

Credit history. An SSN is connected to credit bureau files and is the number most commonly used to build a credit history in the United States. Some financial institutions accept an ITIN for certain banking and credit products, though options may be more limited. We explain this in detail in our guides Can You Open a Bank Account Without a Social Security Number? and How to Build Credit in the U.S. Without a Social Security Number.

How Each Number Is Used When Filing Tax Returns

When we file a federal tax return in the United States, the form requires us to enter a tax identification number. This number tells the IRS who the return belongs to and allows them to match it with their records.

Both an SSN and an ITIN can fulfill this requirement. The tax return forms — Form 1040 for resident filers and Form 1040-NR for nonresident aliens — include a field for the taxpayer identification number, and either an SSN or an ITIN can be entered in that field.

From a structural standpoint, the filing process is essentially the same for SSN holders and ITIN holders. We report income, calculate taxes owed or refundable, and submit the return to the IRS by the annual deadline.

The difference lies not in how the return is filed, but in what the number itself represents and what it is connected to outside of the tax filing context.

One important note for ITIN holders: certain tax credits are only available to individuals with Social Security Numbers. The Earned Income Tax Credit, for example, generally requires an SSN for the taxpayer and qualifying children. Understanding which tax benefits we are eligible for as ITIN holders — and which require an SSN — is an area where working with a qualified tax professional can be particularly valuable.

We provide a broader overview of immigrant tax obligations in our guide Do Immigrants Have to Pay Taxes in the United States?, which explains residency classifications, filing requirements, and the role of the IRS in more detail.

What an ITIN Does Not Do

Because the ITIN is sometimes misunderstood, it is worth being explicit about what it does not provide.

An ITIN does not authorize work in the United States. Presenting an ITIN to an employer as proof of work eligibility is not appropriate and does not satisfy legal employment verification requirements.

An ITIN does not change immigration status. Obtaining or using an ITIN has no direct effect on any immigration application, visa status, or pathway to residency or citizenship.

An ITIN does not provide eligibility for Social Security benefits, Medicare, or most federal assistance programs that require an SSN.

An ITIN does not serve as a government-issued photo ID. It is a tax number only — it does not function as identification for non-tax purposes in the way that a driver’s license or passport does.

Understanding these limits helps us use the ITIN correctly — for its intended purpose of tax compliance — without expecting it to do things it was not designed to do.

Transitioning From ITIN to SSN

For many immigrants, the ITIN is a temporary tool — used during a period when SSN eligibility has not yet been established, and then replaced when circumstances change.

If we obtain work authorization, a green card, or another status that makes us eligible for a Social Security Number, we can apply for an SSN at that point. Once we have an SSN, we use it on all future tax returns instead of the ITIN.

When this transition happens, it is important to notify the IRS so that our tax records — accumulated under the ITIN — can be associated with the new SSN. This ensures continuity in our tax history and prevents complications with IRS records. The IRS provides guidance on this process, and a qualified tax professional can assist with making the transition correctly.

It is worth noting that tax filing history accumulated under an ITIN — years of returns, income documentation, and compliance records — does not disappear when we transition to an SSN. That history remains part of our financial record and can be valuable documentation going forward.

Why Tax Identification Numbers Matter

Beyond the mechanics of filing a return, having and using the correct tax identification number serves an important broader function.

Tax records are documentation. Every return we file creates a verifiable record of income earned, taxes paid, and financial activity during that year. These records can be requested as official transcripts from the IRS and used as evidence of income history in a wide range of contexts — banking, housing applications, and certain financial and immigration processes.

For immigrants who are building financial lives in the United States, this documentation is genuinely valuable. It establishes a paper trail of financial responsibility that institutions and processes can reference. We discuss how income documentation connects to financial services in our guides How to Choose Your First Bank Account in the U.S. and How to Create Your First Budget in the U.S.

Engaging with the tax system — using whichever identification number applies to our situation — is one of the most concrete steps we can take toward building that documented financial foundation.

Conclusion

The Social Security Number and the Individual Taxpayer Identification Number both serve as tax identification numbers in the United States — but they come from different agencies, serve different populations, and carry very different functions beyond the tax filing itself.

An SSN is a broad identification number connected to employment, Social Security benefits, and credit, issued to citizens and certain authorized workers by the Social Security Administration. An ITIN is a tax-specific number issued by the IRS for individuals who have U.S. tax obligations but do not qualify for an SSN.

Both allow us to file tax returns and fulfill our obligations to the IRS. Knowing which one applies to our situation — and understanding what each one does and does not provide — helps us navigate the U.S. tax system accurately and without unnecessary confusion.

MARVODYN provides financial education for informational purposes only. This content is not legal advice or tax advice. Tax identification rules, ITIN eligibility requirements, and IRS regulations may change over time. Individual circumstances vary. Please consult a qualified tax professional or visit irs.gov for guidance specific to your situation. See our full disclaimer at marvodyn.com.