Well, almost could be another year in Social Security Time!
I have only applied for SSDI, not supplemental income (SSI). These are just my experiences, not the rule of law here.
You will receive a Notice of Award letter from SSDI once they make a final determination with either an approval, and why, or a denial, and why. They will send one to you, and one to your attorney. I received my copy before the atty.s office. It will state the date back to which you were approved. If your atty has told you what your estimated monthly benefit will be (they should have), you will be able to roughly estimate what your "lump" award should be.
Your letter will also tell you when you became eligible for Medicare part A (hospitalization insurance) and Medicare part B (medical insurance). You may be able to contact medical providers and have them rebill to Medicare if you did not have insurance coverage previously.
It will take 6-8 weeks after that letter to get your lump award check. If you have not done so, ask your atty to set up direct deposit for you. My husband and I felt like it was Christmas morning when we checked the account one morning and found a windfall in there.
Your monthly benefit is paid once a month, one month in arrears - or one month behind. Februarys' income for me will be paid at the end of March. They will deduct taxes and payment for the Medicare Part B insurance from this check.
I'm not sure how Medicare works. I have insurance coverage through my husbands employer, and so opted out of the Medicare Part B insurance. It will add another 95.00 per month to my check, and my husbands insurance will always be primary. Medicare will not pay for my co-pays or anything else my husbands insurance does not cover, so it made no sense for me to keep it.
I'm sure there are many others who have more experience with this than I, but hope you could glean something out of all this rambling!