In addition to meeting our definition of disability, you must have worked long enough--and recently enough--under Social Security to qualify for disability benefits.

Social Security work credits are based on your total yearly wages or self-employment income. You can earn up to four credits each year.

The amount needed for a credit changes from year to year. In 2014, for example, you earn one credit for each $1,200 of wages or self-employment income. When you've earned $4,800, you've earned your four credits for the year.

The number of work credits you need to qualify for disability benefits depends on your age when you become disabled. Generally, you need 40 credits, 20 of which were earned in the last 10 years ending with the year you become disabled. However, younger workers may qualify with fewer credits.

IMPORTANT: Remember that whatever your age is, you must have earned the required number of work credits within a certain period ending with the time you become disabled. If you qualify now but you stop working under Social Security, you may not continue to meet the disability work requirement in the future.

Let's look at the other requirements: