I file for my parents.they have fixed income.they are not required to file.mom over paid ss so get a return. do i still file married jointly and leave his info blank?

If you are preparing a joint return for your parents you enter ALL of their income, from whatever sources it came from.

Can you explain more?  How did she overpay ss?  Why does she get a refund?  If they file a return (and Joint is the best way)  enter everything for both of them.  Both their SSA-1099 from Social Security and any 1099 forms they get like 1099R and 1099Int etc.