According to the Social Security Administration (SSA), a person qualifies for SSDI if:

  • they have a physical or mental condition that prevents them from engaging in any “substantial gainful activity” (“SGA”), and
  • the condition is expected to last at least 12 months or result in death, and
  • they are under the age of 65, and
  • generally, they have accumulated 20 social security credits in the last 10 years prior to the onset of disability (normally four credits per full or partial year); one additional credit is required for every year by which the worker’s age exceeds 42.

The work requirement is waived for applicants who can prove that they became disabled at or before the age of 22, as these individuals may be allowed to collect on their parent’s or parents’ work credits. The parent(s) experience no loss of benefits.

Medical evidence is signs, symptoms and laboratory findings and is required to document the claim. Symptoms, such as pain, are considered but must be reasonably expected to come from a medically determinable impairment which the claimant is diagnosed to have. The decision is based on a sequential evaluation of medical evidence. The sequence for adults is: 1. Is the claimant performing a Substantial Gainful Activity? If yes, deny. If no, continue to next sequence. 2. Is the claimant’s impairment severe? If no, deny. If yes, continue to next sequence. 3. Does the impairment meet or equal the severity of impairments in the Listing of Impairments? . If yes, allow the claim. If no, continue to next sequence. 4. Is the claimant able to perform past work? If yes, deny. If no continue to next sequence. 5. Is the claimant able to perform any work in the economy? If yes, deny. If no allow the claim.

Medical evidence that demonstrates the applicant’s inability to work is required. The DDS or ALJ may also require the applicant to visit a third-party physician for medical documentation, often to supplement the evidence treating sources do not supply. The applicant may meet a SSA medical listing for their condition. If their condition does not meet the requirements of a listing, their residual functional capacity is considered, along with their age, past relevant work, and education, in determining their ability to perform either their past work, or other work generally available in the national economy.

Determination of a residual functional capacity—made in the fourth step in the sequential evaluation process—often constitutes the bulk of the SSDI application and appeal process. A residual functional capacity is assessed in accordance with Title 20 of the Code of Federal Regulations, part 404, section 1545[4] by a disability determination service (DDS) or, on appeal, by an administrative law judge (ALJ), and is generally based upon the opinions of treating and examining physicians, if available.

Residual functional capacity (RFC) is classified according to the five exertional levels of work defined in the Dictionary of Occupational Titles, which are: Sedentary, Light, Medium, Heavy, and Very Heavy. If the residual funcational capacity of an individual equals the previous work performed, the claim is denied on the basis that the individual can return to former work. If the residual functional capacity is less than former work then the RFC is applied against a vocational grid that considers the individual’s age, education and transferrability of formerly learned and used skills. The vocational grid directs an allowance or denial of benefits.