Onset Date (Alleged vs. Established)

The onset date is the date your disability began. The alleged onset date (AOD) is the date you claim in your application, often the day you stopped working or suffered a major medical event. The established onset date (EOD) is the date SSA ultimately finds supported by the evidence after reviewing your records.

The distinction matters because the established onset date controls when your benefits begin and how much back pay you receive, and for SSDI it must fall on or before your date last insured. SSA sometimes approves a claim but sets a later onset than alleged, which reduces past-due benefits. Choosing a well-supported onset date, and contesting an unfavorable one, can be worth many months of payments.