Beginning with the July 1, 2006 calendar quarter, the IRS interest rates will go up slightly. For corporations, the overpayment rate will be 7% (up from 6%). For overpayments exceeding $10,000, corporations will receive 5.5% interest (up from 4.5%). On the flip side, interest rates for small corporate underpayments will be 8% (up from 7%); and 10% for the larger overpayments (up from 9%).

For individual taxpayers, the rate for under- and over-payments will be 8% (up from 7%).