Workers who are no longer able to work as a result of their disabling medical condition. Eligibility is based on work history (using a credits system) and severity of disability. To qualify, you generally need to have worked in jobs covered by Social Security for at least 5 of the past 10 years (or have 40 credits, 20 of which were earned in the last 10 years), ending the year your disability began. In some cases, usually with younger workers, applicants may be eligible with fewer credits. You also need to meet the definition of disability as outlined by Social Security.