An identification number is a string of digits assigned to you by a government agency or organization to track you in their system

You don't have one identification number — you have several, and each one serves a different purpose. Your Social Security number tracks your work history and tax records with the federal government. Your driver's license number identifies you to your state's motor vehicle department. Your passport number is how the State Department knows who you are when you travel internationally. Banks assign you account numbers. Your employer gives you an employee ID. The IRS uses a different identifier if you're self-employed.

The reason you have multiple numbers is that each organization needs its own way to find your records quickly. When you apply for a job, the employer doesn't look you up by your driver's license number — they use your Social Security number because that's what connects to your tax withholding and background check. When you renew your car registration, the DMV uses your driver's license number because that's what their system recognizes.

Understanding which number does what matters because it affects what information you need to provide in different situations, and it helps you spot when someone is asking for something they shouldn't need.

Key Takeaways

  • Your Social Security number is the primary identifier the federal government uses for tax, employment, and benefits records, and it's the number most vulnerable to misuse.
  • State identification numbers (driver's license, state ID card) are separate from your Social Security number and are used mainly for age verification and driving records.
  • Employer identification numbers (EINs) and individual taxpayer identification numbers (ITINs) are specialized numbers for specific tax or work situations, not general identity numbers.
  • You should never give out your Social Security number unless you're opening a financial account, applying for credit, or dealing with government agencies that specifically request it.

Your Social Security Number and Why It's the Most Important One

Your Social Security number is a nine-digit identifier issued by the Social Security Administration (SSA). It was originally created to track Social Security benefits, but it became the de facto national identification number in the United States because so many systems adopted it.

This number connects to your earnings record, your tax filings, your credit history, and your background. When you start a job, your employer uses your Social Security number to report your wages to the IRS and to verify you're authorized to work. When you apply for a credit card, the bank uses it to pull your credit report. When you apply for a mortgage, a car loan, or a rental apartment, the lender or landlord uses it to check your financial history.

Because your Social Security number opens so many doors to your financial and employment records, it's also the number that identity thieves target most aggressively. If someone has your Social Security number, they can open credit accounts in your name, file a false tax return, or claim benefits fraudulently. This is why you should treat it as sensitive information and only provide it when you're certain the organization has a legitimate reason to request it.

State-Issued Identification Numbers

Your driver's license number and state ID card number are issued by your state's Department of Motor Vehicles (or equivalent agency). These are separate from your Social Security number and serve a different purpose: they prove your identity and age to local authorities and businesses.

A driver's license number is tied to your driving record — traffic violations, accidents, license suspensions. A state ID card number works the same way but is issued to people who don't drive. Neither of these numbers connects to your federal tax records or employment history the way your Social Security number does.

Businesses ask for your driver's license when they need to verify your age (at a bar, for example) or confirm your identity for a transaction. They're not using it to check your credit or employment — they're checking it against their own records or against a database of suspended or revoked licenses. You can safely provide your driver's license number in these situations because it doesn't expose your financial records.

Specialized Numbers for Specific Situations

If you're self-employed or own a business, you have an Employer Identification Number (EIN), also called a Federal Employer Identification Number (FEIN). This is a nine-digit number issued by the IRS that works like a Social Security number for your business. You use it on business tax returns, to open a business bank account, and to hire employees. It's not a personal identifier — it's a business identifier.

If you're not a U.S. citizen but need to file taxes or open a bank account, you may have an Individual Taxpayer Identification Number (ITIN). This is a nine-digit number issued by the IRS that functions like a Social Security number for tax purposes only. You can't use an ITIN to work legally in the United States, but you can use it to file taxes, claim refunds, or open certain bank accounts.

Your bank assigns you an account number for each account you hold with them. This number is specific to that bank and that account — it's not shared across banks. Your employer assigns you an employee ID number that's used only within that company's payroll and HR systems. These numbers are narrow in scope and low in sensitivity because they don't connect to your broader financial or legal identity.

Passport Numbers and Travel Identification

Your passport number is issued by the U.S. State Department and is used to identify you when you travel internationally or apply for a visa. It's a nine-character identifier (a mix of letters and numbers) that's unique to your passport document.

Your passport number is sensitive because it connects to your travel history and your citizenship status, but it's not as widely used as your Social Security number. You provide it when you book international flights, apply for visas, or cross international borders. You should not provide it for domestic transactions or to businesses that have no reason to verify your travel status.

When Someone Asks for an Identification Number

Before you provide any identification number, ask yourself: does this organization have a legitimate reason to request it? A bank opening a savings account needs your Social Security number because they're required by federal law to verify your identity and report interest income to the IRS. A retail store asking for your Social Security number at checkout does not have a legitimate reason — they're asking for something they shouldn't need.

Here's a practical guide: your Social Security number should be requested only by employers, banks, credit card companies, mortgage lenders, the IRS, government agencies, and healthcare providers (for billing purposes). Your driver's license number should be requested when you're proving your age or identity to a local authority or business. Your passport number should be requested only when you're traveling internationally or applying for a visa. If someone asks for a number outside these contexts, you can ask why they need it and refuse if the reason doesn't make sense.

If you're unsure whether a request is legitimate, you can call the organization directly using a phone number from their official website (not a number they provided in the request) and ask whether they actually need that information.

How Identification Numbers Are Protected

Organizations that hold your identification numbers are required by law to protect them. Banks must encrypt your Social Security number in their systems and limit who can access it. The IRS must keep your tax records confidential. Your employer must secure your Social Security number in their payroll system. These are legal obligations, not optional practices.

However, data breaches happen. If a company's systems are compromised, your identification numbers can be exposed. This is why monitoring your credit report and your tax records is important — it helps you catch fraudulent activity early. You can check your credit report for free once a year at annualcreditreport.com (the official site run by the three major credit bureaus). You can create an account at irs.gov to monitor your tax records and watch for fraudulent filings.

Frequently Asked Questions

Can I refuse to give my Social Security number?

You can refuse, but the organization can also refuse to do business with you. If you're opening a bank account or applying for credit, they're legally required to request it for identity verification and fraud prevention. If a retail store or doctor's office asks for it, you can ask why they need it — many times they don't, and you can decline. If they say it's required, you can take your business elsewhere.

What should I do if I think my identification number has been stolen?

If you suspect your Social Security number has been compromised, contact the Social Security Administration at 1-800-772-1213 or visit ssa.gov. If you suspect identity theft, file a report at identitytheft.gov, which is run by the Federal Trade Commission. If your driver's license number has been stolen, contact your state's DMV. Each agency can help you monitor for fraudulent use and take steps to protect your records.

Why do I need different identification numbers instead of just one?

Different organizations need different numbers because they manage different systems and different types of records. Your state doesn't have access to your federal tax records, so they use a different number to track your driving history. Your bank doesn't need to know about your driving record, so they use an account number instead. This separation actually protects you — if one organization's database is breached, not all your records are exposed at once.

Is it safe to put my identification number on a form I'm mailing?

Mailing sensitive information is riskier than providing it online through an encrypted connection, but sometimes it's necessary. If you must mail a form with your Social Security number, send it via certified mail so you have proof of delivery. Better yet, ask the organization if you can provide the number by phone or through their secure online portal instead. Many organizations now offer these alternatives specifically to reduce the risk of mail theft.