The number of work credits required to be eligible for SSDI may vary based on the age at which a worker becomes disabled. A total of 40 work credits could be typically required. 20 out of those 40 credits must have been earned within the last ten years prior to becoming disabled. This could translate roughly into a requirement that an individual must have worked a minimum of five out of the last ten years. There may be special exceptions to this general rule for blind persons and younger persons.