As you probably know by now, the process of applying for and getting SSDI benefits can take many months, especially if the applicant must appeal an initial denial of benefits.  However, applicants may be entitled to back pay from the date of the application and for a period of up to 12 months before the date of the application. 

Here is an example of how the process might work: Let's say you applied for SSDI on January 25, 2009 after being injured on December 29, 2008.  At some point in the approval process, the SSA (either a disability examiner or an Administrative Law Judge) will determine the 'established onset date' of your disability.  Your back pay will be calculated using this onset date, adjusted by the mandatory five month waiting period. (Because SSDI benefits are supposed to be for those who have long-term disabilities, the Social Security Administration will not make disability payments to anyone who has not been disabled continuously for five full months and will not make any payments for those initial 5 months of disability.)     

So, if at a hearing on January 10, 2010 the SSA determines that you are entitled to benefits (after also determining that your established onset date was December 29, 2008, the date you suffered your injury), your date of entitlement would be June of 2009 (date of onset plus five full months).  In this example, you would receive back pay for the period of time beginning in June of 2009 and continuing through January 2010.

As to how long you will have to wait for your back pay, there is no way of knowing. It can take months.  I have also read that the wait can be even longer if your benefits were awarded by a federal judge after a disability hearing.  For more information or to post a question, visit our MA SSDI Discussion Forum.   Good luck.