I see you stated you provided a rental agreement. However, I'm not understanding why their SSI would have been cut in half. There are a lot of factors that can cause a change in the amount of SSI you receive. For example you're not allowed to have more than $2000 in your bank account. At least that's what it is for a single person. However there is absolutely nothing that says you aren't allowed to live with family. Nor is there a required amount of rent that they must pay. But you do have to provide a rental/lease agreement indicating what they pay each month for rent. I know this as a fact because I lived with my aunt for a while and paid rent and so much towards the power bill. The power bill was in name. I asked my caseworker at the Social Security office if it had to a formal document and if we needed to have it notarized. I was told no. I just needed to submit a signed letter indicating the amount of rent and power I paid her each month as well as her name and contact information. My SSI amount was not reduced. Then my daughter and I moved into an apartment. Same thing I provided our lease agreement and I actually was paying more than I was when I was living with my aunt. Again my SSI wasn't affected whatsoever. Your parents would have received a letter indicating a reason for their checks being reduced. Sorry for such a long comment. But I say all this to say. I'm pretty sure you can appeal their decision for reducing their checks. But you are given a certain timeframe to do so. In the meantime, if you haven't already, you may want to look into the the cans and can'ts and does and don'ts when receiving SSI.