You should apply for disability benefits as soon as you become disabled. It can take a long time to process an application for disability benefits (three to five months). If you apply for:
Social Security, disability benefits will not begin until the sixth full month of disability. The Social Security disability waiting period begins with the first full month after the date it is decided that your disability began.
Supplemental Security Income (SSI), SSI disability benefits are paid for the first full month after the date you filed your claim, or, if later, the date you become eligible for SSI.