SSDI back pay is the benefits you should have received during the time your application is under consideration, including time that you were incorrectly denied (if that applies to you.) Receiving disability benefits is usually a long process. Getting your case approved can take anywhere from several months to several years.
To calculate back pay, you need to know the date that you were considered disabled. This date is taken from your medical records. There is a five month waiting period from the date that you became disabled that you are not eligible for benefits. Back pay can usually be given starting at the end of the fifth month after your disability occurs until your application is approved. Back pay is limited to a 12 month maximum. The back pay equation is the number of months you have been disabled before approval minus 5 months (waiting period) and this may not equal more than 12 months. For example, if you were first disabled on January 2nd, you are not eligible for benefits until May 2nd because of the waiting period. You would be able to collect benefits from May 2nd up to May 2nd of the next year because you cannot exceed 12 months.
SSDI benefits back pay is paid in one lump sum. It is hard to determine when that lump sum will be received. There are no set guidelines that state the time frame when the Social Security Administration must pay this amount. The back pay may be paid before your regular benefits begin or it may not be received until after you are have been approved for ongoing benefits and have started receiving benefit checks.