Yes, there is no payroll on Sch C for owners. As I saw you state he did this by error. Did he issue a W-2 for himself? Did he file his payroll reports for this "salary"? You are stating he withheld too much re: medicare. So, if you look at the W-2, does his medicare total $348? If its higher than that is what he over withheld. This assumes I understand what you speak of.