There is a very big IF here. IF YOU GET A FAVORABLE DECISION AND IF THE ONSET DATE IS DETERMINED TO BE 2005. Neither one may happen.

But, if it did, SSA will not be withholding your income tax and will not be paying your outstanding medical bills. Depending upon your date of onset and date of entitlement, you may be entitled to retroactive Medicare and you may be able submit unpaid bills to Medicare for partial payment, if it is covered by Medicare.

What will also happen is that all the SSI you have been paid will be paid back from any SSDI due for the same months and your current SSI benefits will either be reduced or stopped.

And you should have started your own post.