Backpay may be possible in both Social Security Disability Insurance (SSDI) cases as well as Supplemental Security Income (SSI) cases. However, the backpay rules and limits are different for both SSDI and SSI. In order to calculate the full amount of backpay possible in an SSDI case, you must look at your alleged onset of disability (AOD) and your date of filing (DOF). Your AOD is generally the day you became unable to work. Your DOF is the date you filed your application for benefits. Your AOD must be prior to your DOF in order to receive some sort of backpay. Generally, you may receive up to 12 months of retroactive benefits from your DOF. However, it is important to note that SSDI has a five month waiting period. This means they do not pay you for five months after your AOD. Therefore, your AOD would have to be 17 months prior to your DOF in order to get the maximum 12 months retroactive benefits. For example, if your AOD was 01/17/19 and your DOF was 11/17/20, you could receive the maximum backpay of 12 months. You would be eligible for backpay starting 11/17/19. However, if your AOD was 03/17/20 and your DOF 11/17/20 then you would only be eligible for 3 months backpay. There would be a five month waiting prior after AOD so you would be eligible for backpay from 08/17/20. SSI cases have simpler rules to calculate backpay. In SSI cases, Social Security will award backpay only from the first full month after your DOF. Unlike SSDI, no retroactive benefits are allowed from AOD to DOF. Additionally, there is no 5 month waiting period in calculating SSI backpay. It is important to note that these are maximum amounts that an individual is eligible for based on the dates in their application. A judge may find you disabled at a different date, or the judge or your attorney may recommend amending your AOD. These changes to AOD will likely affect the amount of SSDI backpay an individual may be eligible for. Overall, it is crucial to work with an experienced attorney who can explain how the dates in your case may affect any backpay you may be entitled to.