Social Security Disability Insurance (SSDI) allows workers who become disabled to receive the equivalent of their Social Security retirement benefits early. In order for you to apply for SSDI, you need to have enough work credits based on taxable employment to be covered for Social Security purposes. Unlike SSI, because SSDI is based on FICA (Federal Insurance Contributions Act) taxes, you have paid throughout your working career, how much money you have or do not have is not taken into account. The amount of your benefit will be determined by SSA and is dependent upon how much you and your employer(s) have paid into FICA.