WI AB1029

Imposes a Wisconsin estate tax on property transfers at death, effective November 1, 2026, with graduated rates of 0% (below ~$5 million), 6.67% (~$5-10 million), 13.33% (~$10-15 million), and 20% (above $15 million), based on fractions of the federal exclusion amount

Exempts qualifying farmland valued at $15 million or less from the taxable estate if inherited by family members who continuously hold and use it for farming for at least 10 years; selling or developing the land within 10 years triggers full taxation

Requires estate tax returns to be filed within 9 months of death with a 6-month extension available; failure to file incurs a penalty of 5% of tax due or $500 (whichever is less), and unpaid taxes accrue 12% annual interest

Allows installment payments matching federal estate tax schedules under IRC Section 6166, requiring security through liens or financial guarantee bonds

Establishes interstate arbitration procedures to resolve disputes when multiple states claim a decedent as a resident, with panel determinations binding for state death tax purposes