An identification number is a string of digits assigned to you by a government agency or organization to track your records
You don't have one identification number — you have several, and each one serves a different purpose. Your Social Security number identifies you to the federal government for tax and benefits purposes. Your driver's license number identifies you to your state for driving privileges. Your passport number identifies you internationally for travel. Banks assign you account numbers. Your employer assigns you an employee ID. Each number exists in a separate system, held by a separate organization, for a separate reason.
The confusion happens because people often use "identification number" to mean "Social Security number" specifically, since that's the number most frequently requested and most widely misused. But understanding what each of your numbers actually does — and who holds it — is the first step in protecting them.
Key Takeaways
- You have multiple identification numbers issued by different organizations: your Social Security number (federal), driver's license number (state), passport number (federal), and numbers assigned by banks, employers, and other institutions.
- Your Social Security number is the most sensitive because it's used for tax filing, credit reports, and benefits — and it's the one most commonly stolen for fraud.
- Not every organization that asks for your identification number actually needs it; you can ask what it will be used for and whether you can provide an alternative.
- Identification numbers are stored in separate systems by separate organizations, so a breach at one place does not automatically expose all your numbers.
The main identification numbers you're likely to encounter
Social Security number (SSN) is a nine-digit number issued by the Social Security Administration. It's used by the IRS for tax filing, by employers to report your wages, by banks and credit card companies to check your credit history, and by government agencies to administer benefits like Medicare and unemployment insurance. Because it's so widely used, it's the number most frequently targeted by identity thieves.
Driver's license number is issued by your state's Department of Motor Vehicles. It identifies you for driving privileges and is often used as a secondary form of identification when you're in person — at a bank, a doctor's office, or a store checking your age. Each state's format is different; some use letters and numbers, some use only numbers.
Passport number is issued by the U.S. State Department and identifies you for international travel. It's a nine-character combination of numbers and letters. You only need one if you travel outside the United States or its territories.
Tax Identification Number (TIN) is a catch-all term for any number the IRS uses to identify you for tax purposes. Your Social Security number is your TIN if you're a U.S. citizen or permanent resident. If you're not may be able to access for a Social Security number but need to file taxes or open a bank account, you can get an Individual Taxpayer Identification Number (ITIN) instead.
Numbers issued by private organizations
Banks, credit card companies, insurance companies, and employers all assign you numbers. Your bank account number identifies your specific account. Your credit card number is specific to that card. Your insurance policy number identifies your coverage. Your employee ID number identifies you within your employer's system.
These numbers are stored in private databases, not government ones. A breach at your bank doesn't expose your Social Security number unless you've given the bank permission to use it — which you usually have, because banks need it to report interest income to the IRS and to check your credit history before lending you money.
Why organizations ask for identification numbers
A legitimate reason to ask for your Social Security number is to report income to the IRS, to check your credit history, or to verify you're not on a government exclusion list (like someone who owes back taxes or child support). Banks, employers, and government agencies do this regularly and legally.
A weak reason — one you can push back on — is "we need it for our records" or "it's our policy." Many organizations ask for your Social Security number out of habit, not necessity. Retail stores, doctors' offices, and utility companies often ask for it but don't actually need it. You can ask what the number will be used for and whether you can provide your driver's license number instead. Many will accept the alternative.
A red flag is an unsolicited request for your Social Security number by phone, email, or text. The IRS, Social Security Administration, and legitimate banks will not contact you first asking for this information.
How identification numbers are stored and who can access them
Each organization that holds one of your numbers keeps it in its own database. The IRS has your Social Security number. Your bank has your account number and your Social Security number. Your state DMV has your driver's license number. These databases are separate, which means a data breach at one organization doesn't automatically expose all your numbers.
However, because your Social Security number is so widely used, a breach that exposes it can be particularly damaging. If a credit card company's database is breached and your Social Security number is in it, a thief can use that number to open new accounts in your name, file a false tax return, or explore for benefits.
Government agencies and private companies are required by law to protect these numbers with encryption and access controls. In practice, the level of protection varies. Large banks and the federal government generally have stronger security than small businesses or medical offices.
What to do if an identification number is compromised
If you learn that your Social Security number has been exposed in a data breach, you have several options. You can place a credit freeze with the three major credit bureaus (Equifax, Experian, and TransUnion), which prevents anyone from opening new credit accounts in your name without your permission. You can also sign up for credit monitoring, which alerts you if new accounts are opened or inquiries are made on your credit report.
If your driver's license number is compromised, contact your state's DMV. They can issue you a new number and flag your account for fraud. If your passport number is compromised, contact the State Department's passport office.
If you suspect someone has used your Social Security number to file a false tax return or claim benefits, report it to the IRS and the Social Security Administration directly. Both have fraud hotlines and online reporting tools.
Frequently Asked Questions
Can someone open a credit card with just my identification number?
Not with just the number alone — they would also need your name, address, and date of birth, which are often available from public records or data breaches. That's why a single compromised number is less dangerous than multiple pieces of information exposed together. A credit freeze prevents new accounts from being opened even if someone has all this information.
Why do so many places ask for my Social Security number when I'm just buying something?
Most don't actually need it. Retail stores, restaurants, and utility companies often ask out of habit or because their system is set up to collect it. You can decline and provide your driver's license instead. The only time you're legally required to provide your Social Security number is when income is involved (a job, a bank account, a loan) or when a government agency requests it.
Is it safe to carry my Social Security card in my wallet?
No. Your Social Security card is a document, not an ID you need to show regularly. Keep it in a safe place at home — a safe, a locked drawer, or a safe deposit box. You only need the number itself, which you can memorize or write down separately. If your card is lost or stolen, contact the Social Security Administration to report it.
What's the difference between an ITIN and a Social Security number?
An ITIN (Individual Taxpayer Identification Number) is issued by the IRS to people who need to file taxes but aren't may be able to access for a Social Security number — typically non-citizens or undocumented immigrants. It's formatted like a Social Security number (nine digits) and serves the same purpose for tax filing, but it's not tied to work authorization or benefits may be able to access the way a Social Security number is.
Can I change my Social Security number if I'm worried about identity theft?
Yes, but only in limited circumstances. The Social Security Administration allows you to change your number if you can document that you're being harassed or if you're a victim of identity theft. The process takes time and requires proof. A credit freeze is usually a faster and more effective way to prevent new accounts from being opened in your name.