With identity theft and cyber crime on the rise, it’s no wonder so many Americans are now questioning when it is and isn’t appropriate to give an institution or business their full Social Security number.

Virtually every major financial or health decision requires you to hand over your Social Security number (SSN). Banks require it to open accounts, loans, or credit cards in your name, and doctors, health insurers, and hospitals use it more for billing purposes.

These aren’t the only institutions asking for access to your SSN: universities, government agencies, employers, utility providers, landlords, and even some retailers will ask, but not every organization asking for your SSN necessarily NEEDS it. And in fact, in some cases, you’re better off if you don’t give it.

So, who NEEDS my Social Security number?

Businesses and organizations that report to or otherwise deal directly with the Internal Revenue Service (IRS) regarding your transactions with them will always ask you for your full SSN. In other words, if a company credit-reports or credit-checks, they’re going to need the number.

This includes credit-reporting bureaus, banking institutions during home purchases, car purchases, or credit card and account openings, some utility providers, insurance companies, landlords when you’re applying to rent an apartment, investment advisors, and your employer.

Federal law also says tax authorities, the Department of Motor Vehicles, and federal agencies have a right to ask for your SSN to identify you, though The Privacy Act of 1974 mandates that all government agencies from local to federal level notify citizens whether or not requests for their SSNs are required.

For more information about the kinds of places you’ll have to provide your SSN, here is a list compiled by the Social Security Administration detailing many of the agencies and organizations where giving your SSN is required by law.

When should I refuse to give my Social Security number?

This piece over at CBS Pittsburgh provides some helpful tips when it comes to choosing when you should give someone your SSN. In an interview with Andrew Richards, fraud expert at Fraud Investigative Service in Pittsburgh, Richards recommends keeping three questions in mind when prompted to give your SSN:

Did you reach out to them or did they reach out to you? If you’ve initiated an inquiry, service, or purchase wherein you’re asked for your SSN, it’s likely the request is more trustworthy than if someone contacts you out of the blue to request it. In the case of requests made via email, online forms, or phone calls, this is especially true–most if not all reputable organizations asking for this information will never do so using these methods.

Do you know why they need it? You are always within your rights to ask someone why he needs your SSN. Someone prompting you for your SSN should be able to tell you why he needs it without hesitation. If the reason isn’t something that has to do with legitimate and required reporting to the IRS (such as simple identification), it might be best to ask for an alternative method to identify yourself without giving your full number.

Do they need your full SSN? If an organization simply needs to identify you, ask if it’s possible to use a partial SSN to do so. Many legitimate businesses and agencies only need you to verify the last four digits of your SSN along with some other information to satisfy identification requirements. It may also be wise to ask the organization if you can identify yourself through other means.

The Social Security Administration itself says a person can refuse to give his SSN to a private business at any time, but that a refusal to do so may result in a failure to receive services.