“My Mom is on SSI and just recently got a divorce from my Dad. He sent me a check but it is made out to my Mom. I am wanting to know if she signs it over to me will it affect her SSI? We live in Del Norte County, California.”
Since this is not income to her – she is merely signing it over to you – it does not seem to be income that would be countable for your mother. If your father wants to send you money in the future, he should write the checks directly to you. If this amount is court ordered child support, then it would be reportable income to the SSA that may decrease the SSI benefit.