The onset date is the official date, as determined by the Social Security Administration (SSA), that a Social Security Disability Insurance (SSDI) applicant became disabled. The onset date is also the start of the five-month waiting period before Social Security Disability Insurance payments begin. This waiting period only applies to SSDI and not Supplemental Security Income (SSI). The official onset date is important, as it will determine the amount of disability backpay the recipient is entitled to. The onset date will be set by examining the claimant’s work history and medical records.
The earlier the onset date is established, the greater the backpay award will be, however, backpay in SSDI cases will not be paid for any period earlier than 12 months prior to the date of the application for benefits, regardless of the onset date. SSI backpay will only extend back to the date the application is filed with SSA. In most cases, the SSDI beneficiaries will receive their entire backpay award in one payment, whereas large SSI backpay awards may be split into as many as three installments.