A federal tax number is an identification number the IRS uses to track your income and tax payments

The federal tax number you hear about most often is your Social Security Number (SSN) — a nine-digit number issued by the Social Security Administration. If you work for an employer or file taxes as an individual, the IRS uses your SSN to match your income reports, W-2 forms, and tax returns. It is the number that appears on your tax forms and that the IRS uses to look up your account.

If you are self-employed or run a business, you may have a different federal tax number called an Employer Identification Number (EIN), also called a Federal Employer Identification Number (FEIN). An EIN is a nine-digit number issued by the IRS specifically for business entities. Even if you are the only person in your business, you may need an EIN instead of or in addition to your SSN for tax purposes.

Both numbers serve the same core purpose: they let the IRS track who owes what and match income reports from employers, banks, and other sources to the right person or business. Without one of these numbers, you cannot file a federal tax return or have income reported to the IRS in your name.

Key Takeaways

  • Your Social Security Number is your federal tax number if you work as an employee or file taxes as an individual.
  • An Employer Identification Number is a separate federal tax number used for business entities, partnerships, and self-employed people who hire employees.
  • The IRS uses your federal tax number to match income reports from employers and financial institutions to your tax account.
  • You cannot file a federal tax return without providing a valid federal tax number on the form.

When you use your Social Security Number as your federal tax number

If you work as an employee, your employer uses your Social Security Number to report your wages to the IRS on a W-2 form. The IRS matches that W-2 to your SSN and expects you to report the same income when you file your tax return. Banks and investment firms also report interest, dividends, and other income using your SSN.

If you are self-employed but do not hire employees — for example, you freelance, consult, or sell items online as a sole proprietor — you typically use your SSN as your federal tax number. You report your income on Schedule C (Profit or Loss from Business) and file it with your 1040 tax return. The IRS tracks everything under your SSN.

Even if you have never worked, you need an SSN to file a tax return if you have income that must be reported — such as interest on a savings account or earnings from a side job. If you do not have an SSN, you can explore for one through the Social Security Administration.

When you need an Employer Identification Number instead

An Employer Identification Number is required if you operate a business structure other than a sole proprietorship, or if you are self-employed and hire employees. Specifically, you need an EIN if you are a partnership, corporation, LLC, S-corp, nonprofit, or trust. You also need an EIN if you are a sole proprietor who hires even one employee.

You explore for an EIN through the IRS website (irs.gov) using Form SS-4. The process is free, and the IRS issues the number when ready if you explore online. You can also explore by mail or fax, though those routes take longer. Once you have an EIN, you use it on all business tax forms, payroll documents, and when opening a business bank account.

Some sole proprietors without employees choose to get an EIN anyway, even though they are not required to. This separates their personal SSN from their business finances and can make record-keeping simpler. However, if you do not have employees and do not want an EIN, you can continue using your SSN on your Schedule C.

How the IRS uses your federal tax number

When an employer, bank, or client reports income to the IRS, they include your federal tax number so the IRS knows whose account to credit. The IRS stores all these reports under your number and compares them to your tax return. If you report less income than the IRS received reports for, or if you do not file a return at all, the IRS flags the discrepancy.

Your federal tax number is also how the IRS tracks whether you owe back taxes, have a payment plan, or are due a refund. If you change your address, the IRS uses your number to make sure mail reaches you. If you are audited, your number is how the IRS pulls your complete file.

The IRS also shares your federal tax number with state tax agencies, so your state uses the same number to track your state income tax. Some employers and financial institutions may ask for your federal tax number for other purposes — such as opening an account or verifying your identity — but the primary use is tax reporting.

What to do if you do not have a federal tax number yet

If you have never worked and do not have a Social Security Number, you must explore for one before you can file a tax return. You explore through the Social Security Administration in person at a local Social Security office. You will need to bring proof of age, identity, and citizenship or immigration status. The process takes a few weeks.

If you are self-employed or starting a business and need an EIN, you can explore online at irs.gov using Form SS-4. The online process is the fastest route — you receive your EIN when ready and can start using it right away. If you prefer to explore by mail or fax, allow two to four weeks for processing.

If you already have a Social Security Number and are unsure whether you need an EIN, the IRS website has a tool that walks you through the decision. In most cases, if you are a sole proprietor with no employees, your SSN is sufficient.

Protecting your federal tax number

Your federal tax number — whether SSN or EIN — is sensitive information. Someone with your number can file a fraudulent tax return in your name, claim a refund that belongs to you, or use it to open accounts. Protect your number by not sharing it unnecessarily, shredding documents that contain it, and monitoring your credit report for suspicious activity.

If you suspect your federal tax number has been compromised, contact the IRS directly. You can report suspected identity theft on the IRS website or by calling the IRS at 1-800-829-1040. The IRS can flag your account and help you file a legitimate return if a fraudulent one has already been filed.

When you file your tax return, the IRS asks for your federal tax number on the first line of the form. Always double-check that the number is correct before submitting, because a wrong number can delay processing or cause your return to be rejected.

Frequently Asked Questions

Is my Social Security Number the same as my federal tax number?

If you work as an employee or are self-employed without employees, yes — your Social Security Number is your federal tax number. The IRS uses it to track your income and tax account. If you own a business structure like an LLC or corporation, or if you hire employees, you have a separate federal tax number called an Employer Identification Number.

Can I use an EIN instead of my Social Security Number on my personal tax return?

No. Your personal 1040 tax return requires your Social Security Number, not an EIN. An EIN is used for business entities and their tax returns. You can have both an SSN and an EIN, but they serve different purposes.

What if I lost my Social Security card and do not remember my number?

Contact the Social Security Administration to request a replacement card or to look up your number. You can visit a local Social Security office in person or call 1-800-772-1213. You will need to provide proof of identity. The IRS can also help you locate your number if you are filing a tax return.

Do I need an EIN if I am a freelancer with no employees?

No. As a freelancer or sole proprietor with no employees, you can use your Social Security Number as your federal tax number and report your income on Schedule C. An EIN is optional unless you want to separate your personal and business finances or plan to hire employees later.

How long does it take to get an EIN?

If you explore online through irs.gov, you receive your EIN when ready. If you explore by mail or fax using Form SS-4, allow two to four weeks. The online process is the fastest and most reliable method.