WI SB1012

Replaces fixed interest rates on late, nondelinquent taxes (currently 12% per year) and tax refunds (currently 3% per year) with a variable rate determined annually by the Department of Revenue based on the Federal Reserve Bank of New York's effective federal funds rate published on January 2 of each year

Beginning in 2026, DOR must calculate a monthly interest rate by adding 1 to the federal funds rate, raising it to the power of one-twelfth, and subtracting 1, then publish this rate on its website

Applies to individual and corporate income taxes, franchise taxes, withholding taxes, sales and use taxes, utility and insurer taxes, motor fuel excise taxes, alcohol beverage taxes, cigarette/tobacco/vapor product taxes, economic development surcharge, petroleum inspection fees, and metalliferous mining taxes

Changes the reduced interest rate for delinquent income and franchise taxes (when the Secretary of Revenue determines reduction is fair and equitable) from the fixed 12% per year to the new variable rate

First applies to assessments issued and refunds paid on or after January 3, 2026, regardless of the taxable periods involved