A federal tax number is your identification for the IRS
A federal tax number is a nine-digit identifier the Internal Revenue Service assigns to you so it can track your income, taxes, and tax filings. The IRS uses it to match your tax returns, W-2 forms, 1099 forms, and other documents to your account. Without one, you cannot file a federal tax return or claim income on your record.
The most common federal tax number is your Social Security Number (SSN), which you get from the Social Security Administration. If you do not have an SSN — because you are not a U.S. citizen or permanent resident — you can get an Individual Taxpayer Identification Number (ITIN) from the IRS instead. Both serve the same purpose with the IRS: they link your income and tax obligations to your identity.
You need a federal tax number to work legally in the United States, file taxes, open a bank account, get a mortgage, or claim a child as a dependent. Employers ask for it on the I-9 form before you start work. The IRS uses it to enforce tax law and prevent fraud.
Key Takeaways
- A federal tax number is a nine-digit code the IRS uses to identify you for tax purposes, and it is either your Social Security Number or an Individual Taxpayer Identification Number.
- Your Social Security Number is issued by the Social Security Administration and is the standard federal tax number for U.S. citizens and permanent residents.
- An ITIN is the federal tax number for people who are not may be able to access for a Social Security Number but still need to file taxes or claim income in the United States.
- You must provide your federal tax number to your employer, your bank, and the IRS when you file a return or report income.
Social Security Number versus ITIN
A Social Security Number is issued by the Social Security Administration to U.S. citizens, permanent residents, and certain temporary visa holders. It is a nine-digit number that starts with an area number, a group number, and a serial number. The SSN is the primary federal tax number and also serves as your identifier for Social Security benefits, Medicare, and other government programs.
An Individual Taxpayer Identification Number (ITIN) is issued by the IRS to people who do not have an SSN but need to file taxes or report income. This includes nonresident aliens, undocumented immigrants, and some visa holders. An ITIN is also nine digits and looks similar to an SSN, but it always starts with the number 9. You cannot use an ITIN to work legally or to claim Social Security benefits — it is for tax purposes only.
Both numbers work the same way with the IRS: they link your income, deductions, and tax liability to your identity. The difference is who can get one and what else you can use it for. If you are may be able to access for an SSN, you should get one instead of an ITIN, because an SSN opens more doors.
How to get a federal tax number
To get a Social Security Number, you explore through the Social Security Administration in person at your local Social Security office. You will need proof of age (a birth certificate or passport), proof of citizenship or legal residency (a passport, green card, or visa), and proof of identity. The SSN is free and usually arrives by mail within two weeks.
To get an ITIN, you file Form W-7 with the IRS. You can mail it in or file it through a tax professional or community organization that is authorized to help. You will need to prove your identity and your reason for needing an ITIN — usually a copy of your tax return or a letter explaining why you need to file. The IRS processes ITINs by mail and typically takes four to six weeks.
If you already have a federal tax number, you do not need to get a new one. The number stays with you for life, even if you move, change jobs, or change your name. You only need to update your name with the Social Security Administration or IRS if you legally change it.
Why employers and banks ask for your federal tax number
Your employer asks for your federal tax number on the I-9 form and the W-4 form so they can report your wages to the IRS under your name. The IRS matches the W-2 form your employer sends with your tax return to make sure you reported all your income. If the numbers do not match, the IRS will contact you.
Banks and credit card companies ask for your federal tax number to report interest income and to verify your identity. The IRS receives copies of these reports and uses them to cross-check your tax return. If you earned interest but did not report it, the IRS will know.
Landlords, mortgage lenders, and investment firms also ask for your federal tax number for the same reason: to report income or payments to the IRS under your name. Refusing to provide it can result in penalties or being denied the service.
What happens if you do not have a federal tax number
If you work without a federal tax number, your employer cannot legally hire you and cannot report your wages to the IRS. You cannot file a tax return, claim a refund, or claim dependents. You cannot open a bank account at most institutions or get a loan.
If you are self-employed or have income from other sources and do not have a federal tax number, you still owe taxes on that income. The IRS can assess penalties and interest if you do not file. If someone reports income under your name without your knowledge, you will need a federal tax number to file and correct the record.
If you are undocumented or do not have an SSN, getting an ITIN allows you to file taxes, claim refunds, and report income legally. Many people use an ITIN to build a tax history and demonstrate financial responsibility, which can help with future immigration cases or loan applications.
Federal tax number and identity theft
Your federal tax number is sensitive information. Protect it the way you would protect a password. Do not carry your Social Security card in your wallet, do not post it online, and do not give it to someone unless you know why they need it and that they are legitimate.
If someone uses your federal tax number to file a false tax return or claim a refund in your name, you will need to report it to the IRS and the Federal Trade Commission. The IRS has a process for victims of tax identity theft, and you can file Form 14039 to alert them. Check your credit report regularly for accounts you did not open.
If you suspect your federal tax number has been compromised, contact the IRS Identity Theft Hotline at 1-800-908-4490 or visit IdentityTheft.gov to file a report.
Frequently Asked Questions
Is a federal tax number the same as a Social Security Number?
A Social Security Number is a type of federal tax number, but not all federal tax numbers are Social Security Numbers. If you have an SSN, that is your federal tax number. If you do not have an SSN but have an ITIN, that is your federal tax number. Both work with the IRS the same way.
Can I get a federal tax number without being a U.S. citizen?
Yes. If you are not a U.S. citizen or permanent resident, you can get an ITIN from the IRS. You will need to file Form W-7 and provide proof of identity and a reason for needing the number, such as filing a tax return or claiming income.
What if I lost my Social Security card?
You do not need the card itself — the IRS and your employer only need the number. You can find your number on past tax returns, W-2 forms, or bank statements. If you need a replacement card, contact the Social Security Administration at 1-800-772-1213 or visit ssa.gov.
Do I need a federal tax number if I do not work?
If you have no income, you do not need a federal tax number to exist. However, if you have any income — wages, self-employment income, interest, or rental income — you need one to report it. If you have a child, you need a federal tax number for them to claim them as a dependent on your return.
How long does it take to get a federal tax number?
A Social Security Number usually takes two weeks to arrive by mail after you explore in person. An ITIN takes four to six weeks when you mail Form W-7 to the IRS. Some tax professionals can file Form W-7 electronically, which can speed up the process.