Social Security Disability Insurance (SSDI) pays monthly benefits to you if you're disabled and unable to work. If you're approved for SSDI, you might be able to get past (or "retroactive") benefits from before you applied for SSDI. Here's how it works.
Your "onset date" is when your disability began—when your impairment first prevented you from working. The date the Social Security Administration (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 might be able to get past benefits or back pay.
Your EOD will be the date the SSA determines all of the following became true:
It's important to know that the EOD isn't 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 your condition became severe enough to qualify you as "disabled" for SSDI purposes, but you might not have met other eligibility criteria on that date.
You won't receive benefits immediately after the SSA determines your EOD. When figuring out how far back you'll be paid benefits, you have to keep in mind that there is a waiting period. The SSA requires you to wait five months after your EOD before you can get benefits.
But because of the way the SSA counts time, your waiting period can last longer than five 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 doesn't count in your five-month waiting period. Your waiting period would be February, March, April, May, and June. Your benefits would start on July 1.
The SSA won't pay you more than 12 months of retroactive benefits—no matter how long ago you became disabled. Since there's also a five-month waiting period, figuring out your retroactive benefits isn't always a simple process. Here are some examples to help clarify:
If you applied for SSDI benefits on October 1, 2021, and the SSA gives you an EOD of January 2, 2021, you would get retroactive benefits from July 1, 2021. You wouldn't receive benefits for January, February, March, April, May, or June of 2021 because of the waiting period. (The SSA would have begun counting the five months starting on February 1, 2021.)
If you applied for SSDI on October 1, 2021, and your EOD is January 2, 2020, your five-month waiting period would have ended on July 1, 2020. But you wouldn't get retroactive benefits all the way back to July 1, 2020, because the SSA only allows retroactive payments for up to 12 months before your application date. So, you'd only get benefits back to October 1, 2020.
There are two exceptions to the waiting period rule. First, if you're eligible for SSDI benefits as the child of a disabled person, you don't have the five-month waiting period.
The second exception is for people whose benefits stop and then start again. There's no five-month waiting period the second time around.
For instance, let's say you were approved for SSDI benefits three years ago but then improved and went back to work. Your benefits would have stopped after your trial work period. If you become disabled again, you wouldn't have to wait five months from your new EOD until you could again receive benefits. (This exception only applies if it's been five years or less between your first EOD and your second.)
It can take several months to a year or more for your SSDI claim to be approved. Once it's approved and your five-month waiting period is over, you should receive your SSDI back pay (usually at the same time you receive your first monthly check). These payments are generally made in one lump sum (unlike SSI back pay, which is usually paid in installments).
The SSDI claims process can be complex. You might need to hire an attorney to help you get the SSA to approve your benefits. If you do, and you get approved, your attorney would be paid out of your back pay lump sum.
For more information about SSDI, including back pay, check out Nolo's Guide to Social Security Disability, by David Morton III, M.D.
Updated April 19, 2022