The Social Security number was originally devised to keep an accurate record of each individual’s earnings, and to subsequently monitor benefits paid under the Social Security program. However, use of the Social Security number as a general identifier has grown to the point where it is the most commonly used and convenient identifier for all types of record-keeping systems in the United States.
Specific laws require a person to provide his or her Social Security number for certain purposes. While we cannot give you a comprehensive list of all situations where a Social Security number might be required or requested, a Social Security number is required or requested by the following organizations:
· Internal Revenue Service for tax returns and federal loans;
· Employers for wage and tax reporting purposes;
· Employers enrolled in E-Verify;
· States for the school lunch program;
· Banks for monetary transactions;
· Veterans Administration as a hospital admission number;
· Department of Labor for workers’ compensation;
· Department of Education for Student Loans;
· States to administer any tax, general public assistance, motor vehicle or drivers license law within its jurisdiction;
· States for child support enforcement;
· States for commercial drivers’ licenses;
· States for Food Stamps;
· States for Medicaid;
· States for Unemployment Compensation;
· States for Temporary Assistance to Needy Families; or
· U.S. Treasury for U.S. Savings Bonds
The Privacy Act regulates the use of Social Security numbers by government agencies. When a federal, state, or local government agency asks an individual to disclose his or her Social Security number, the Privacy Act requires the agency to inform the person of the following: the statutory or other authority for requesting the information; whether disclosure is mandatory or voluntary; what uses will be made of the information; and the consequences, if any, of failure to provide the information.
If a business or other enterprise asks you for your Social Security number, you can refuse to give it. However, that may mean doing without the purchase or service for which your number was requested. For example, utility companies and other services ask for a Social Security number, but do not need it; they can do a credit check or identify the person in their records by alternative means.
Giving your Social Security number is voluntary, even when you are asked for the number directly. If requested, you should ask why your Social Security number is needed, how your number will be used, what law requires you to give your number and what the consequences are if you refuse. The answers to these questions can help you decide if you want to give your Social Security number. The decision is yours.
from the social security government site -- see the link below.