IRS interest rates will remain unchanged for the calendar quarter beginning April 1, 2021. The rates will be:
- 3% for overpayments (2% in the case of a corporation);
- 0.5% for the portion of a corporate overpayment exceeding $10,000;
- 3% for underpayments; and
- 5% for large corporate underpayments.
For taxpayers other than corporations, the overpayment and underpayment rate is the federal short-term rate plus 3 percentage points. This rate is determined by the IRS on a quarterly basis.