For paper-filed returns does a copy of form SSA-1099 have to be attached to F-1040 if there was federal income tax withheld? The instructions to F-1040 don't really say, but seem to imply from the absence of any mention of that form that it does not need to be attached. Does anyone know for sure? Do you attach ... or not? Since the SSA sends only one copy of form SSA-1099, if a copy is attached to F-1040, it would have to be a photocopy.