A Social Security number is important, because the federal government uses it to keep track of how much your yearly wages are (and how much tax you owe in federal income taxes). For this reason, one of the first questions after being hired is often, "What is your Social Security number?" Your employer must note this number on his payroll and will use this number to disclose the amount of federal taxes withheld from your paycheck, and sends his part of the required taxes to the Internal Revenue Service (IRS).

A valid social security card may be required in other circumstances. These include:

Loans

When you are filing your tax returns for the IRS

When you apply for a federal loan or for Student

When opening a bank account

Most states also require a Social Security number when applying for a drivers license, although in some circumstances this can be waived. Applying for state public assistance such as Food Stamps, Medicaid, Unemployment Compensation,

TANIF (Temporary Assistance to Needy Families) also requires a Social Security Card.

And if you want to buy U.S. Savings bonds from the U.S. Treasury, you will be asked for your Social Security number.

When a government agency asks you for your Social Security number, you are protected by the privacy act, which means that they must disclose to you what use will be made of the number, whether disclosure is voluntary or not, and what consequences will occur (if any) if you don't supply that information.

For instance, a utility companies may ask you for your Social Security number. You
can ask in this situation why they need your number, how it will be used, and what would happen if you refuse, then make a decision whether to give it to them or not.

You do not need a Social Security number if you are a student in order to register for school, and should not be required to get a nonworking one. Schools use Social Security numbers as student identification numbers if they have one, but if not, the school will assign its own number to you for identification.