It is April 28, 2026. Per Revenue Ruling 2026-8, the IRS has officially set the interest rates for the quarter beginning April 1, 2026. For most LLC owners (individuals and partnerships), the rate for underpayments is now 6%.
1. The Cost of Being Late
- The Rates: 6% for underpayments and 6% for overpayments (5% for corporations). Large corporate underpayments are even higher, at 8%.
- Estimated Tax Trap: These rates also apply to estimated tax underpayments for the second quarter of 2026.
- The Shark Insight: “Cheap money is gone. If you’re ‘borrowing’ from the IRS by underpaying your estimates, you’re paying a 6% APR. That’s higher than many business lines of credit (Article #589). Pay your estimates on time using the Article #591 (BTA) to keep that 6% in your pocket.”