It depends on your age. In general, you need 20 work credits, or quarter-years, of employment in the 10 years before applying for SSD and during which time you paid FICA payroll taxes. This work history does not need to be consecutive. For instance, if you have a total of five years of employment during the 10 years before applying for SSD, you should be eligible. If you became disabled before the age of 31, you do not need as many credits.