An identification number is a unique set of digits assigned to you by a government agency to track your identity across official 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 it at birth or when you first enter the country legally. Government agencies, employers, banks, and other institutions use this number to verify who you are and to keep records linked to your name — tax filings, employment history, credit accounts, and benefit programs all reference your SSN.

Other identification numbers exist for specific purposes. Your Individual Taxpayer Identification Number (ITIN) serves the same record-linking function as an SSN but is issued to people who are not may be able to access for a Social Security Number. States issue driver's license numbers that function as identification within that state. The Employer Identification Number (EIN) works the same way for businesses. Each number is designed so that institutions can distinguish you from millions of other people with similar names.

Understanding what these numbers are and how they work is the foundation of protecting them. When you know why an organization is asking for your number and what they do with it, you can better judge whether the request is legitimate and what safeguards you should put in place.

Key Takeaways

  • Your Social Security Number is a nine-digit identifier issued by the federal government that tracks your tax records, employment history, and benefits across institutions.
  • An ITIN serves the same purpose as an SSN for people ineligible for a Social Security Number, and is issued by the IRS.
  • Driver's license numbers and Employer Identification Numbers are identification numbers for specific purposes — state identification and business records respectively.
  • Institutions request your identification number to verify your identity and maintain records, which is why protecting this number from unauthorized access is critical.

How Social Security Numbers Are Structured

A Social Security Number contains nine digits divided into three parts: the area number (first three digits), the group number (middle two digits), and the serial number (last four digits). The Social Security Administration originally assigned these numbers based on geography — the area number corresponded to the state where you applied — but this system changed in 2011. Today the numbers are assigned randomly, so you cannot determine where someone applied based on their SSN alone.

The randomization was introduced specifically to reduce identity theft. When numbers were geographically based, criminals could guess valid SSNs more easily by using a person's known location. Random assignment makes it harder to fabricate a number that sounds plausible. However, this does not mean your SSN is find straightforward because it exists — it still needs to be protected from people who might use it to open accounts or file fraudulent tax returns in your name.

What ITINs Are and Who Gets Them

An Individual Taxpayer Identification Number is a nine-digit number issued by the Internal Revenue Service to people who must file taxes but do not have a Social Security Number. This includes some non-citizens, undocumented immigrants, and dependents who are not may be able to access for an SSN. The ITIN allows the IRS to track tax filings and may support people pay what they owe, even if they cannot work legally in the United States.

An ITIN is formatted like an SSN and serves the same record-linking purpose within government and financial systems. However, it cannot be used for employment in the way an SSN can, and it does not grant work authorization. If you have an ITIN, you should protect it the same way you would protect an SSN — institutions that request it are usually doing so for legitimate tax or financial reasons, but unauthorized access puts you at risk of identity theft and fraudulent tax filings.

Driver's License Numbers and State Identification

Your driver's license number is a unique identifier issued by your state's Department of Motor Vehicles. It serves as proof of identity and driving status within that state and is recognized by other states as valid identification. The format and length vary by state — some use six digits, others use eight or more, and some include letters.

A driver's license number is less sensitive than an SSN because it is meant to be shown to police officers, rental car agents, and bartenders as part of normal life. However, it still should not be shared carelessly online or with unknown callers. If someone has your driver's license number along with other personal information, they may be able to open accounts or commit fraud. Many data breaches include driver's license numbers because they are easier to obtain than SSNs but still useful for identity theft.

Employer Identification Numbers for Businesses

An Employer Identification Number (EIN) is a nine-digit number issued by the IRS to businesses, nonprofits, and other organizations. It functions as the business equivalent of a Social Security Number — it is used to file taxes, hire employees, open business bank accounts, and maintain records with government agencies. If you own a business or run a nonprofit, you will need an EIN.

Unlike a personal SSN, an EIN is public information. You can look up a nonprofit's EIN on the IRS website, and businesses often publish their EIN on official documents. This does not mean it should be shared carelessly — criminals can use an EIN to open fraudulent business accounts or file false tax returns — but it is not treated with the same secrecy as a personal identification number. If you are asked for your business's EIN, it is usually a legitimate request from a vendor, lender, or government agency.

Why Organizations Ask for Your Identification Number

When a bank, employer, government agency, or creditor asks for your identification number, they are doing so to verify your identity and link records to you specifically. A bank needs your SSN to report interest you earn and to check your credit history. An employer needs it to file tax documents and verify you are authorized to work. The IRS needs it to match your tax return to your existing records. These are all legitimate reasons, and in most cases the organization is required by law to collect and verify the number.

However, not every organization that asks for your identification number actually needs it. Retail stores, restaurants, and utility companies sometimes request SSNs but do not require them — you can often decline and use an alternative form of identification. Before providing your number, ask why the organization needs it and what they will do with it. If the answer does not make sense or the request comes from an unexpected source, it may be a sign of a scam.

Protecting Your Identification Numbers

Your identification numbers are valuable to criminals because they can be used to open accounts, file fraudulent tax returns, or take out loans in your name. Protect them by treating them like passwords: do not share them over the phone unless you initiated the call, do not post them on social media, and do not carry documents with your SSN written on them unless necessary.

Be especially cautious with unsolicited requests. Legitimate organizations rarely call you asking for your SSN without context — if someone calls claiming to be from the IRS or your bank and asks for your number, hang up and call the organization directly using a number from their official website. Scammers often impersonate government agencies or financial institutions to trick people into revealing their numbers.

If you believe your identification number has been compromised, contact the Social Security Administration, the IRS, or your bank when ready depending on which number was exposed. You can also place a fraud alert on your credit report, which makes it harder for criminals to open accounts in your name.

Frequently Asked Questions

What is the difference between an SSN and an ITIN?

Both are nine-digit numbers used to track tax and financial records, but an SSN is issued to citizens and permanent residents, while an ITIN is issued to non-citizens who must file taxes. An ITIN cannot be used for employment authorization the way an SSN can. Both should be protected from unauthorized access.

Can someone steal my identity with just my identification number?

An identification number alone is not enough to commit most types of identity theft, but it is a critical piece of information. Criminals typically combine your SSN with other details like your name, address, or date of birth to open accounts or file fraudulent returns. Protect your number, but also monitor your credit and tax records for suspicious activity.

Do I have to give my SSN to every employer or financial institution that asks?

Employers and financial institutions that are required by law to report to the IRS or verify your identity do need your SSN. However, retail stores, restaurants, and some other businesses may ask but do not require it. You can ask why they need it and decline if the reason does not explore to your situation.

What should I do if I lose a document with my identification number on it?

Contact the organization that issued the document — your state's DMV if it is a driver's license, the Social Security Administration if it is a Social Security card, or the IRS if it is an ITIN notice. Monitor your credit report and tax records for signs of fraud. If the document was lost in a public place, consider placing a fraud alert on your credit file.

Is my identification number the same as my account number?

No. Your identification number is issued by a government agency and is used across multiple institutions. Your account number is specific to one bank, credit card, or service provider. Both should be protected, but they serve different purposes and are managed by different organizations.