A Tax Identification Number Is How the IRS Tracks You

A Tax Identification Number (TIN) is a nine-digit code the Internal Revenue Service uses to identify you for tax purposes. It functions as your tax record identifier — the IRS uses it to match your income reports, tax returns, and payment history. You need one to file taxes, open a business, hire employees, or claim certain tax credits.

The most common type of TIN is a Social Security Number (SSN), which you get from the Social Security Administration. If you are not a U.S. citizen or do not have an SSN, you can get an Individual Taxpayer Identification Number (ITIN) from the IRS instead. Businesses and self-employed people use an Employer Identification Number (EIN). Each type serves the same basic purpose: giving the IRS a way to track tax obligations and match documents.

Key Takeaways

  • A Tax Identification Number is a nine-digit code the IRS uses to identify you on tax records, income reports, and returns.
  • Social Security Numbers are the most common TIN for individuals; ITINs are for non-citizens or people without an SSN; EINs are for businesses and self-employed people.
  • You need a TIN to file a tax return, claim tax credits, open a business bank account, or hire employees.
  • Getting an SSN or ITIN takes time — plan ahead if you need one before tax season.

The Three Main Types of Tax Identification Numbers

Social Security Numbers (SSN) are issued by the Social Security Administration to U.S. citizens, permanent residents, and certain temporary visa holders. You receive one automatically as a newborn if your parents provide a Social Security number on your birth certificate, or you can request one later. An SSN is the default TIN for most people filing taxes in the United States.

Individual Taxpayer Identification Numbers (ITIN) are issued by the IRS to people who are not may be able to access for an SSN but need to file taxes or claim credits. This includes non-citizens, undocumented immigrants, and some visa holders. An ITIN looks like a Social Security Number — nine digits — but starts with a 9. You request an ITIN by filing Form W-7 with the IRS, along with proof of identity and residency status.

Employer Identification Numbers (EIN) are nine-digit codes for businesses, partnerships, nonprofits, and self-employed people. The IRS issues them to identify business entities for tax purposes. You need an EIN if you hire employees, operate as a corporation or partnership, or run a business that files certain types of tax returns. You can request an EIN online from the IRS website at no cost, and you receive it immediately.

When You Need a Tax Identification Number

You need a TIN to file a federal income tax return, even if you do not owe taxes. The IRS requires a TIN on the return itself. You also need one to claim tax credits like the Earned Income Tax Credit (EITC) or the Child Tax Credit, to open a business bank account, to hire employees, and to report income from self-employment or freelance work.

If you are a dependent claimed on someone else's return, you still need your own TIN — your parent or guardian will include it on their return. If you are a non-citizen working in the United States, your employer will ask for your TIN before your first paycheck. If you do not have one yet, you will need to get an ITIN or SSN before you can start work.

How to Get a Social Security Number

If you are a newborn, your parents can request an SSN when they register your birth certificate. If you are an adult and do not have one, you can apply at your local Social Security office. You will need to bring proof of age (a birth certificate or passport), proof of citizenship or immigration status, and a photo ID. The Social Security Administration processes applications in person and typically issues a number within two weeks.

If you are applying by mail, the process takes longer — usually four to six weeks. You can find your nearest Social Security office on the Social Security Administration website. There is no cost to request an SSN.

How to Get an Individual Taxpayer Identification Number

To request an ITIN, you file Form W-7 with the IRS. You must include proof of identity (a passport, national ID card, or driver's license from your home country) and proof of residency in the United States (a utility bill, lease, or bank statement). You can file Form W-7 by mail or in person at an IRS office or an authorized acceptance agent — many nonprofits and tax preparation services are authorized agents.

Processing time varies. If you file by mail, the IRS typically processes your application within four to six weeks. If you file in person at an IRS office or authorized agent, you may receive your ITIN faster. There is no cost to request an ITIN. Once issued, an ITIN is valid for tax purposes as long as you file a tax return at least once every three years.

How to Get an Employer Identification Number

You can request an EIN online through the IRS website at no cost. The online application takes about 15 minutes and you receive your EIN immediately. You can also apply by phone, fax, or mail, but those methods take longer — typically two to four weeks by mail.

To apply, you will need your Social Security Number or ITIN, the legal name of your business, your business address, and information about the type of business structure (sole proprietorship, partnership, corporation, nonprofit, etc.). You do not need to have filed taxes before or have a business license yet. Once you receive your EIN, you can use it to open a business bank account and hire employees.

What Happens If You Do Not Have a Tax Identification Number

If you do not have a TIN and you are required to file taxes, you cannot submit your return to the IRS. The IRS will reject any return that does not include a valid TIN. If you are self-employed or have income from a job, your employer or client may not be able to pay you without one — they need your TIN to report your income to the IRS on a Form 1099 or W-2.

If you are waiting for your TIN to arrive, you can still file your tax return using a temporary number or a notice of application. Contact the IRS or a tax professional for guidance on your specific situation. The sooner you request a TIN, the sooner you can file and claim any refunds or credits you are owed.

Frequently Asked Questions

Can I use my Social Security Number as my business tax ID?

If you are a sole proprietor with no employees, you can use your SSN as your business TIN. However, if you hire employees or operate as a corporation or partnership, you must get an EIN. Many sole proprietors get an EIN anyway to keep their personal and business finances separate.

What if I lose my Social Security card?

You do not need the physical card to use your SSN. Your number itself does not change. If you need a replacement card, you can request one at your local Social Security office or online through the Social Security Administration website. There is no cost for the first nine replacement cards in your lifetime.

How long does it take to get an ITIN?

By mail, the IRS typically processes ITIN applications within four to six weeks. If you file in person at an IRS office or authorized acceptance agent, processing may be faster. Plan ahead if you need your ITIN before tax season.

Do I need a TIN if I do not work?

If you have no income, you do not need a TIN to file taxes. However, if you are claimed as a dependent on someone else's return, that person needs your TIN. If you think you might be owed a refund or tax credit, you should have a TIN so you can file.

Can I change my TIN?

Your Social Security Number and ITIN do not change. If you get married and change your name, you notify the Social Security Administration, but your number stays the same. An EIN also does not change unless your business structure changes significantly.