The interest rate for Medicare overpayments and underpayments went up August 11, rising from 11.625 percent to 12.125 percent, according to a Centers for Medicare & Medicaid Services program memorandum (AB-03-122; http://cms.hhs.gov/manuals/pm_trans/AB03122.pdf). The rate was 12.625 percent at this time last year. In other recent program memoranda, CMS: