Under Medicare regulations,  the interest rate that may be charged on Medicare overpayments and underpayments is the higher of the current value of funds rate (five percent for calendar year 2008) or the private consumer rate as fixed by the Department of the Treasury.  According to a recent CMS Transmittal, the Department of the Treasury has notified the Department of Health and Human Services that the private consumer rate has been changed to 11.375%.  Accordingly, effective as of October 22, 2008, the interest rate that may now be charged on Medicare overpayments and underpayments is 11.375%.