Like most people, you probably don't expect to become disabled. However, according to the Social Security Administration (SSA), studies show that 1 in 4 of today's 20 year-olds will become disabled before reaching full retirement age.1 That's why it's important to understand what disability benefits you may be entitled to under Social Security.

The SSA administers two programs that pay disability benefits. The Social Security Disability Insurance (SSDI) program pays benefits to qualified individuals who are under full retirement age, regardless of their income. The Supplemental Security Income (SSI) program pays benefits to qualified individuals with limited income. Only the SSDI program is discussed here.

Because the definition of disability that the SSA uses is strict, it's hard to qualify for Social Security disability benefits. To receive benefits as an adult, you must have a physical or mental impairment that has lasted or is expected to last for at least 12 months or is expected to result in your death. Your impairment must also be severe enough to prevent you from performing any "substantial gainful activity" or, in other words, the work that you were doing when you became disabled or any other work.

The SSA has a list of impairments that are considered so severe that they automatically define you as disabled. If your condition is not on the list, the SSA must decide if it's severe enough.

When determining your ability to work, the SSA will consider your medical condition, age, education, past work experience, and transferable skills. If you're working, the amount of income that you are able to earn also plays a role. If your average monthly earnings from work exceed a maximum amount set by the SSA, you generally won't be considered disabled for Social Security purposes. Special rules and income limits apply if you're blind.

In general, to get disability benefits, you must meet two different earnings tests. The first is a recent work test, based on your age at the time you became disabled. The second is a duration of work test to show that you worked long enough under Social Security. For a table that illustrates these requirements see SSA Publication 05-10029, Disability Benefits.

If you qualify for disability benefits, certain family members can also collect monthly benefits based on your work record. Eligible family members may include:

• Your spouse age 62 or older, if married at least one year
• Your former spouse age 62 or older (if you were married at least 10 years)
• Your spouse or former spouse of any age, if caring for your child who is under age 16 or disabled
• Your unmarried child under age 18 (or under 19 if still in high school)
• Your unmarried child older than 18 with a qualifying disability that started before age 22

Each eligible family member may receive a monthly check equal to as much as 50 percent of your basic benefit. This is in addition to your benefit — your check doesn't get reduced.

The amount of your monthly disability check is based on your average lifetime earnings. To view your earnings record and get an estimate of how much you would receive if you were disabled right now, sign up for a my Social Security account at the SSA's website, ssa.gov, so that you can view your Social Security Statement.

Eligibility for other state and federal benefits may affect the amount of your SSDI check. And because the SSA will periodically review your case and decide whether you are still disabled, your disability benefits may stop altogether. This will happen if your medical condition improves to the point that you're no longer considered disabled, or if you are able to earn a substantial amount of money. Finally, once you reach full retirement age, your disability benefits will automatically convert to Social Security retirement benefits (the amount is usually the same).

You should apply for benefits as soon as you become disabled, and it appears that the disability will continue. Processing an application can take three to five months. Disability benefits will be paid for the sixth full month after the date your disability began.

You can file for benefits in person, online, or over the phone. You'll be asked to provide information such as your Social Security number, your birth or baptismal certificate, medical records, a work summary, and a copy of your most recent W-2 form, or if you're self-employed, a copy of your federal tax returns for the past year.

Once your application is complete and has been reviewed by your local Social Security office, it will be sent to the Disability Determination Services (DDS) office in your state. There, the DDS will determine whether you are disabled under Social Security rules. If your claim is approved, you'll receive a letter showing the amount of benefit that you'll receive and when your benefits will begin. If your claim is denied, you'll receive a letter explaining the decision and telling you how to appeal if you don't agree with it.

For more information on Social Security disability benefits, visit your local Social Security office, look at publications available on the SSA website, or call the SSA at (800) 772-1213.