Social Security pays benefits to tens of millions of people who are retired or disabled and also to spouses and surviving family members. Eligibility for Social Security is not automatic; you have to work and pay Social Security tax for a minimum amount of time. For people who don’t pay into the Social Security system, there are alternative programs.

Social Security Eligibility

You can’t get Social Security retirement benefits before age 62, but you start on your path to eligibility when you get your first job and begin paying Social Security tax. The Social Security Administration uses a system of credits to determine if a person is entitled to benefits. Forty credits are required. As of 2013, you get one credit for every $1,160 of earnings on which you pay Social Security tax up to a maximum of four credits a year. You can earn credits at any age, and once you get them, you keep them. For example, a high school or college student with a part-time job making $4,640 will accumulate the maximum four credits for a year.

Benefits for Family

A married person who doesn't qualify can still get Social Security up to 50 percent of her spouse’s benefit amount provided she is at least 62 or has a child who is younger than 16 or disabled. When someone dies, the spouse and minor children also can get benefits. Qualifying for survivors benefits may require as few as six credits, depending on the age of the deceased.

Social Security Disability

Social Security pays benefits to people with disabilities if they have worked and paid Social Security tax. If you become disabled, you can get Social Security Disability Insurance benefits with as few as six credits if you are younger than 24. The number of credits required for SSDI rises with age to a maximum of 40 at age 62.

Supplemental Security Income

Despite the scope of the Social Security program, not everyone qualifies. Supplemental Security Income is a program funded by Uncle Sam for people who need income assistance but aren’t eligible for Social Security. SSI payments are paid to disabled children, adults with disabilities who don’t qualify for SSDI and people age 65 and older who don’t have enough credits to receive retirement benefits. As of 2013, the SSI benefit amount was $710 per month for individuals and $1,066 for couples. Individual states may add an additional amount to SSI, so the actual benefit amount may be more.

Social Security Alternatives

Some workers are enrolled in alternative programs instead of Social Security. If you go to work for a railroad, for example, you pay a tax to fund railroad retirement benefits instead of Social Security. A Railroad Retirement benefit must be at least equal to what you’d get from Social Security, but it can be more. Some states also have their own retirement plans for public employees instead of Social Security.