ITIN vs. SSN
Understand the differences between SSNs and ITINs for accurate tax reporting and compliance.
Understanding SSNs and ITINs
Goals and takeaways
- Understand the difference between a Social Security Number (SSN) and an Individual Taxpayer Identification Number (ITIN)
- Know when to collect each type of Tax Identification Number (TIN)
- Learn how SSNs and ITINs are supported in Check
Overview of tax identification numbers
When setting up employees in a payroll product built with Check, Partners are required to collect a valid Tax Identification Number (TIN). There are two common types of TINs:
- Social Security Number (SSN) — issued by the Social Security Administration (SSA)
- Individual Taxpayer Identification Number (ITIN) — issued by the Internal Revenue Service (IRS)
TINs are used to report income and employment tax information to the federal government.
What is an SSN?
An SSN is a nine-digit number issued to U.S. citizens and certain lawful residents. It is used for:
- Employment eligibility and wage reporting
- Social security benefits tracking
- Federal and state tax withholding
Employees who are eligible for an SSN must provide it during onboarding. This is the most common TIN used for payroll purposes.
What is an ITIN?
An ITIN is a nine-digit number issued by the IRS to individuals who are not eligible to receive an SSN but have a federal tax filing requirement. ITINs:
- Begin with the number 9
- Are used only for tax processing
- Do not authorize employment or qualify a person for Social Security benefits
Who might need an ITIN?
- Nonresident aliens required to file a U.S. tax return
- Resident aliens (based on IRS criteria) who are not eligible for an SSN
- Dependents or spouses of U.S. citizens, resident aliens, or nonresident aliens
- Individuals who need to report U.S. income but do not qualify for an SSN
Best practices for collecting TINs in Check
Check’s API supports both SSNs and ITINs as valid TINs for employees.
- Always collect an SSN when the employee is eligible
- Only accept an ITIN if the employee is not eligible for an SSN
Ensuring the appropriate TIN is used helps avoid IRS mismatches or SSA verification errors during payroll tax reporting.
Summary
TIN type matters for compliance and accurate tax reporting. Check allows support for both SSNs and ITINs, but SSNs should be collected whenever possible. Partners should clearly distinguish between the two during onboarding and only use ITINs in situations where an SSN is not permitted by law.
For implementation guidance, refer to Check’s Employee API documentation for field-level specifications.
Last updated on June 6, 2025