Social Security Disability Insurance (SSDI) pays monthly benefits to you if you are disabled and unable to work. If you are approved for SSDI, you may be able to get past, or retroactive, benefits from before you applied for SSDI.
Your "onset date" is when your disability began; that is, when your impairment prevented you from working. The date that the SSA determines to be your onset date is your "established onset date," or EOD. If your EOD is before you applied for SSDI, or before you were approved for benefits, you should be able to obtain past benefits, or backpay.
On the date that the SSA determines all of the following are true, that date will become your EOD:
It is sometimes important to know that the established onset date is not necessarily the date you became disabled, which the SSA sometimes refers to as the "medical onset date," or "MOD." The medical onset date is the date that your impairment became severe enough to qualify you as "disabled" for SSDI purposes, but you may not have met other eligibility criteria on that date.
When figuring out how far back you will be paid benefits, you have to keep in mind that there is a "waiting period." When the SSA determines what your established onset date is, it will not give you benefits immediately after your EOD. The SSA requires that you wait five months after your EOD before you can get benefits. The five months after your EOD are called the "waiting period" and they must be five complete months. Unless your EOD is the very first day of a month, the SSA will wait until the first day of the next month and then start counting the five months you have to wait. For example, if your EOD is January 2, the rest of January does not count in your five-month waiting period. Your waiting period would be February, March, April, May and June. Your benefits would start to be paid July 1.
The SSA will not pay you for more than 12 months of retroactive benefits. Since there is also the five-month waiting period, figuring out your retroactive benefits can be confusing. Using some examples may help clarify.
There are two exceptions. First, if you are eligible for SSDI benefits as the child of a disabled person, you do not have the five month waiting period.
Second, if your benefits start and the stop again, you don't have the five-month waiting period. That is, if you were approved for SSDI benefits some time ago, but then improved and went back to work and your SSDI benefits stopped, but then you became disabled again, you will not have to wait the five months from your EOD until you can receive your benefits. However, the exception applies only if it has been five years or less from your first EOD to your second.