is for individuals who worked and are "insured" by the Social Security taxes (F.I.C.A.) that are withheld from their earnings to replace part of a person's earnings upon retirement, disability, or for survivors when a worker dies. If insured workers (and, in some cases, their dependents or survivors) become disabled, they may become eligible for SSDI benefits. The amount received is dependent upon how many years an individual has worked and the individual must apply to determine if (s)he is eligible for benefits. 67Â See also entitlements.