Relating to: interest rates on late, nondelinquent taxes and on overpayments. (FE)

AB 1026 updates interest rate calculations for tax payments and refunds in Wisconsin. It sets a 1% monthly interest rate (12% annually) on underpaid estimated taxes due between June 15 and payment date, and requires 12% annual interest during tax filing extensions for corporations and pass-through entities. The bill also mandates that the Department of Revenue (DOR) pays 3% annual interest on tax overpayments. These changes affect taxpayers filing returns, including corporations, pass-through entities, and individuals who use federal tax extension periods. The bill clarifies existing interest rate provisions across multiple tax statutes without altering tax obligations.