After an Administrative Law Judge (ALJ) has determined that you are disabled, you will receive a letter from Social Security Administration (SSA) called a Notice of Award. In the award letter, SSA will tell you whether its decision is fully favorable or partially favorable. The letter will also explain the reasons behind the fully or partially favorable decision and state the established onset date explicitly.
The established onset date (EOD) is the day on which SSA believes that you became completely disabled and eligible for disability benefits. As part of your application process, you must allege an onset date, and, in reviewing your file, SSA will determine whether it agrees with your alleged onset date; if not, it will propose an established onset date of its own for a date sometime later than the one that you alleged.
When the ALJ agrees with your alleged onset date, he or she will establish that date as the date your disability began, and you will receive a fully favorable decision. That means you will be entitled to disability benefits from the established onset date forward.
When the ALJ agrees that you are disabled but disagrees with your alleged onset date, he or she will establish a different onset date, and you will receive a partially favorable decision. Again, SSA still believes that you are disabled, just not starting on the date you claim. You will be entitled to disability benefits from the newly-established onset date forward.
Partially favorable decisions are also granted for closed periods of disability. A closed period of disability is a stretch of time lasting for at least twelve consecutive months during which you were completely disabled and unable to work. At some point after that twelve-month period, however, your condition improved, and you are no longer permanently disabled. An ALJ will award you benefits for the period of time from when you became disabled to when you became able to work again. You will not receive ongoing disability benefits.
Sometimes, the difference between the onset date that you alleged in your claim and the date that the ALJ establishes is vast, and the difference in back pay could be thousands of dollars. You do have the right to appeal a partially favorable decision, but doing so is risky: when the Appeals Council takes up your case, they may agree with you, they may agree with the ALJ, or they may determine that you are not disabled at all and not eligible for any benefits.
In the event that you receive a partially favorable decision, contact SSA and ask for your file and records to be sent to you. Then consult with a reputable Social Security disability benefits attorney and ask for a professional opinion on whether or not to pursue an appeal to the Appeals Council. You only have sixty days to appeal from the date printed on your Notice of Award, so act quickly.