How Many People Have Your Social Security Number?

You probably know that you shouldn’t keep your Social Security card in your wallet. But do you know when you actually have to give it to someone who asks?

Social Security numbers are the master keys to your personal data, so it pays to be cautious about who gets to see yours. On the other hand, there are services you can’t access without surrendering that precious information. So who gets it and who doesn’t? And how do you say no?

The easiest way to say no is passively. If a form asks for your Social Security number, see what happens if you just leave it off. For example, schools ask for this information and use it as a student identifier, but there are often alternatives. However, when your student is ready for college, you’re going to have to provide it on the Free Application for Federal Student Aid (FAFSA).

You might also need to give it if you are a Girl Scout cookie chairman (though a recent form offers the safer option of a driver’s license number). Volunteering with children? If a criminal background check is required, they will need your Social Security number.

Credit Checks & Applications

You will definitely have to give your Social Security number when you apply for credit.

That’s one reason to apply at home, or on a secure connection online rather than at the checkout counter when a clerk offers to let you fill out a paper application for a store card (and there are people standing right behind you in line).

Most of your personal financial data can be accessed with your Social Security number. That means every credit card issuer you have, plus anyone else who has given you a loan — or turned you down for one — has your number. It’s important to note that just because a lender has your SSN doesn’t make your identity unsafe, it’s just one more place cybercriminals and other fraudsters can target to get to the cash cow that is your good name.

If you check your credit — a good habit that can help you detect identity theft early — you will need to give your Social Security number. That is true of both the site mandated by federal law for obtaining free annual credit reports (AnnualCreditReport.com) and the free credit scores from Credit.com.

Your doctor and dentist may also ask for it, even if you have an insurance identification number that is different from your Social Security number. If your doctor’s office asks for one, it’s fine to ask your healthcare professional if you can instead assure them that your emergency contact has it and will provide it if necessary. Some insurance companies still use Social Security numbers as identification numbers. In that case, you may be faced with a choice between not using your insurance and giving your Social Security number. You certainly could let your insurer know that you don’t want to put your identity at risk to use your insurance.

But Credit Checks Go Beyond the Credit World

An employer or potential employer will want your Social Security number. Because credit checks are sometimes part of the application process, a company you don’t even work for may have your Social Security card. Your employer should. If you freelance, your clients will also need your Social Security number or Taxpayer Identification Number.

And should you lose your job, you’ll need to give your number to the unemployment office. Government benefits require a Social Security number. (That includes Medicare, and Medicare cards include your Social Security number, which many regard as a major flaw.)

In fact, anyone who might need to report your income to the IRS needs your Social Security number. So add brokerages, banks and companies you have invested in.

Most likely your landlord has your Social Security number, too. He or she needed it to check your credit before accepting you as a tenant.

And finally, when you file your personal tax return you must provide a Social Security number.

So the chances of your Social Security number falling into the wrong hands are hardly minuscule. You can keep your number from being any more widely circulated than it has to be by revealing it only when you are required to do so. Regularly checking your credit has the additional advantage of serving as an alert that your identity may have been compromised. So whether you are trying to build or rebuild credit or just maintain your own good credit, ensuring that the “master key” of your financial information is protected is crucially important.

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This article originally appeared on Credit.com.

Gerri Detweiler is Credit.com's Director of Consumer Education. She focuses on helping people understand their credit and debt, and writes about those issues, as well as financial legislation, budgeting, debt recovery and savings strategies. She is also the co-author of Debt Collection Answers: How to Use Debt Collection Laws to Protect Your Rights, and Reduce Stress: Real-Life Solutions for Solving Your Credit Crisis as well as host of TalkCreditRadio.com.