An identification number is a unique set of digits assigned to you by a government agency to track your identity across records

The most common identification number in the United States is your Social Security Number (SSN), a nine-digit code issued by the Social Security Administration. You receive one when you're born, when you become a permanent resident, or when you're authorized to work. Other identification numbers exist too — your driver's license number, passport number, and state ID number are all forms of identification — but the SSN is the one most widely used by banks, employers, government agencies, and credit bureaus to verify who you are.

An identification number serves as a shorthand. Instead of writing out your full name, address, and birth date every time you open a bank account or file taxes, institutions use your number to pull up your existing records. This speeds up transactions and reduces paperwork. The downside is that if someone obtains your identification number, they can potentially access accounts, take out loans, or file taxes in your name.

Key Takeaways

  • Your Social Security Number is a nine-digit identifier issued by the federal government and used by banks, employers, and credit agencies to track your financial and employment history.
  • You receive an SSN at birth, when you become a permanent resident, or when you're authorized to work in the United States.
  • Other identification numbers — like driver's license and passport numbers — serve similar purposes but are issued by different agencies for specific uses.
  • Protecting your identification number is critical because criminals can use it to open accounts, apply for credit, or file fraudulent tax returns in your name.
  • You should never share your identification number unless you're certain the request comes from a legitimate institution you already do business with.

How your Social Security Number is structured

A Social Security Number has three parts: the area number (first three digits), the group number (middle two digits), and the serial number (last four digits). The area number originally indicated the state where you applied for the SSN, though that connection is no longer strict. The group and serial numbers are assigned in a specific pattern to prevent duplication.

The SSN itself does not contain encoded information about your age, gender, or citizenship — it is simply a unique identifier. However, the structure does allow the Social Security Administration to verify that a number follows the correct format, which is one reason why scammers sometimes use obviously fake SSNs when committing fraud.

Who issues identification numbers and when

The Social Security Administration issues SSNs to U.S. citizens, permanent residents, and people authorized to work in the country. You typically receive one shortly after birth if your parents apply, or later when you become a permanent resident or gain work authorization. You can also apply for an SSN in person at your local Social Security office if you don't have one.

Other government agencies issue their own identification numbers for specific purposes. Your state's Department of Motor Vehicles issues a driver's license number when you get a license or ID card. The State Department issues a passport number when you apply for a passport. These numbers are not interchangeable — each serves a different function and is maintained by a different agency.

Why institutions ask for your identification number

Banks ask for your SSN before opening a checking or savings account because they report account activity to the IRS and credit bureaus under that number. Employers request it to report your wages and withhold taxes. Credit card companies use it to pull your credit report and decide whether to approve you. Insurance companies use it to verify your identity and check your claims history. In each case, the institution is legally required to collect and verify the number before doing business with you.

Government agencies — the IRS, state tax authorities, and benefits programs — also require your SSN to match you to your tax records, income history, and any benefits you receive. When you file taxes, apply for a mortgage, or claim unemployment, your SSN is how the system confirms you are who you say you are.

The difference between identification numbers and personal information

Your identification number is not the same as your personal information, though they are related. Personal information includes your name, address, phone number, email, and date of birth. Your identification number is a code that links to all of that information in government and private databases.

A scammer who has only your name and address cannot do much damage. A scammer who has your identification number can access or create accounts in your name, apply for credit, file a false tax return, or claim benefits fraudulently. This is why your identification number is treated as sensitive information — it is the key that unlocks access to your financial and legal identity.

What to do if you lose track of your identification number

If you forget your Social Security Number, you can find it on tax documents, W-2 forms, bank statements, or previous loan applications. You can also contact the Social Security Administration directly by calling 1-800-772-1213 or visiting your local Social Security office in person with a photo ID and proof of citizenship or permanent residency.

If you suspect someone else has your identification number and may be using it fraudulently, contact the Social Security Administration's fraud hotline at 1-800-269-0271. You can also place a fraud alert with the three major credit bureaus (Equifax, Experian, and TransUnion) by calling any one of them, and they will notify the others. A fraud alert tells lenders to verify your identity before opening new accounts in your name.

How to protect your identification number

Never share your identification number over the phone, email, or text message unless you initiated the contact and are certain you are speaking with a legitimate institution. Scammers often call or email claiming to be from the IRS, Social Security Administration, or your bank, asking you to "verify" your number. Real government agencies and established businesses will not ask for your SSN this way.

Keep documents containing your identification number in a safe place — a locked drawer, safe, or safe deposit box. Shred documents before throwing them away. When you apply for credit or services, ask why the institution needs your number and whether they can use an alternative identifier. Some businesses will accept a driver's license number instead of an SSN if you ask.

Monitor your credit report regularly by visiting AnnualCreditReport.com, where you can view your report from all three bureaus once per year at no cost. If you see accounts you did not open, dispute them immediately with the credit bureau and the institution that opened the account.

Frequently Asked Questions

What is the difference between a Social Security Number and a Tax ID Number?

A Social Security Number is issued to individuals and is used for employment, credit, and benefits. A Tax ID Number (also called an Employer Identification Number or EIN) is issued to businesses and is used for business taxes and payroll. If you are self-employed, you may have both — an SSN for personal taxes and an EIN for your business.

Can I change my Social Security Number?

Yes, but only in limited circumstances. The Social Security Administration will issue a new number if you can show that your current number has been misused, that you are a victim of identity theft, or that you have religious or cultural objections to your number. You must apply in person at a Social Security office with documentation of your situation.

Do I need to memorize my identification number?

You should know your Social Security Number, but you do not need to memorize it. Write it down and store it securely. Memorizing it is helpful if you apply for jobs or credit frequently, but it is not required. Never write it on documents you carry with you daily, like your wallet or purse.

What happens if someone uses my identification number?

Contact the Social Security Administration's fraud hotline at 1-800-269-0271 immediately. Place a fraud alert with the credit bureaus, check your credit report for unauthorized accounts, and file a report with the Federal Trade Commission at IdentityTheft.gov. Keep records of all fraudulent accounts and disputes you file.

Is my identification number the same as my PIN or password?

No. Your identification number is a permanent code issued by the government. A PIN or password is something you create and can change. Never use your identification number as a password, and never share your identification number with anyone who asks for a password.