If you are a non-U.S. resident who needs to file taxes in the United States, it is important to understand itin vs ssn. These two numbers are often confused, but they serve very different purposes. Choosing the wrong one can delay your tax filings, cause IRS compliance issues, and create unnecessary stress. Knowing which identification number applies to your situation is the first step in ensuring a smooth, compliant tax process.

This guide explains what ITINs and SSNs are, how they differ, who is eligible for each, and how non-U.S. residents can determine the correct number to apply for.

What Is a Social Security Number (SSN)?

A Social Security Number (SSN) is a nine-digit number issued by the Social Security Administration (SSA). Its main purpose is to track workers’ earnings and calculate Social Security benefits. Over time, the SSN has become a central form of identification in the United States, used for employment, taxes, banking, credit, and government programs.

SSNs are issued to:

• U.S. citizens

• Lawful permanent residents (green card holders)

• Non-U.S. residents who are authorized to work in the United States

If you work legally in the U.S., your employer will use your SSN to report wages, withhold payroll taxes, and meet federal employment requirements.

What Is an Individual Taxpayer Identification Number (ITIN)?

An Individual Taxpayer Identification Number (ITIN) is issued by the Internal Revenue Service (IRS) to individuals who need to file a U.S. tax return but are not eligible for an SSN. ITINs always begin with the number 9 and follow a specific IRS format.

ITINs are commonly issued to:

• Nonresident aliens required to file U.S. taxes

• Spouses and dependents of U.S. taxpayers

• Foreign investors receiving U.S.-source income

• Resident aliens who cannot obtain an SSN

Unlike an SSN, an ITIN is used exclusively for federal tax purposes. It does not allow employment, provide immigration benefits, or qualify the holder for Social Security benefits.

ITIN vs SSN: Main Differences

While both ITINs and SSNs are tax identification numbers, there are key differences that non-U.S. residents must understand:

Purpose:

• SSN: Employment, tax reporting, and government benefits

• ITIN: Tax filing and reporting only

Eligibility:

• SSN: Individuals with authorization to work in the U.S.

• ITIN: Individuals who cannot obtain an SSN but have tax obligations

Issuing Authority:

• SSN: Social Security Administration

• ITIN: Internal Revenue Service

Work Authorization:

• SSN: Allows legal employment

• ITIN: Does not permit work

Validity:

• SSN: Permanent

• ITIN: Can expire if unused for three consecutive years on tax returns

Understanding these differences is essential to avoid errors and IRS complications.

Who Should Apply for an SSN?

Non-U.S. residents should apply for an SSN if they:

• Are authorized to work in the U.S.

• Earn wages from a U.S. employer

• Are subject to Social Security and Medicare taxes

Having an SSN allows employers to process payroll correctly and ensures accurate tax reporting.

Who Should Apply for an ITIN?

An ITIN is appropriate if you:

• Must file a U.S. tax return but cannot get an SSN

• Earn U.S.-source income from investments, rental property, or business activities

• Are listed as a dependent or spouse on a U.S. tax return

• Have U.S. tax reporting obligations without employment authorization

Applying for the wrong number can delay processing and create compliance issues, so it’s critical to evaluate your eligibility carefully.