What is SSDI?
SSDI is short for Social Security Disability Insurance. In general, SSDI pays monthly cash benefits to people who are unable to work for a year or more because of a disability. After a 24-month waiting period, SSDI eligibility allows you to receive Medicare benefits even if you are under age 65.

Qualifying for SSDI
To qualify for benefits, you must first have worked in jobs covered by Social Security. You must also have a medical condition that meets the Social Security Administration's (SSA) definition of disability. In addition to meeting the definition of disability established by SSA, 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 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.

What is SSI?
SSI is short for Supplemental Security Income. It pays monthly cash benefits to people who are age 65 or older, those who are blind, or those who have a disability and who do not own much or have a lot of income. SSI is not just for adults. Monthly benefits can go to disabled and blind children, too.
The amount of cash benefits you can receive depends on the state in which you live. The basic SSI amount is the same nationwide. However, many states add money to the basic benefit. Call the Social Security Administration at 800-772-1213 to find out the benefit amount for your state.

Qualifying for SSI benefits
To qualify for SSI benefits, you have to meet a variety of eligibility requirements, including an income and resource test on where you live.  

How is disability defined by Social Security?
The Social Security Administration’s (SSA) definition of disability is different than other programs you may come into contact with through your employer or private insurance. The SSA pays only for total disability. No benefits are payable for partial disability or for short-term disability.
Eligibility to SSD/SSI  is based on your inability to work. You are generally considered disabled by the SSA if:

• You cannot do work that you did previously;
• It is determined that you cannot adjust to other work because of your medical condition(s); and
• Your disability has lasted or is expected to last for at least one year or result in death.