ID S1120

Applies to wills and trusts of decedents dying between December 31, 2009 and January 1, 2011 that contain formula clauses referencing "unified credit," "estate tax exemption," "applicable exemption amount," or similar federal estate and generation-skipping transfer tax provisions.

Deems such formula clauses to refer to federal tax laws as they applied on December 31, 2009 in 2010, unless the decedent's will or trust was executed or amended after December 31, 2009 with contrary intent.

Allows personal representatives, trustees, fiduciaries, or affected beneficiaries to petition the court within 12 months of the decedent's death to determine if the decedent intended different tax law treatment, with the court able to modify provisions to conform to the decedent's intent or tax objectives.

Permits interested persons to enter into binding nonjudicial agreements to determine the decedent's intent and conform terms without court approval, or to petition the court to approve such agreements.

Declares an emergency and provides the act shall take effect retroactively to January 1, 2010, applying to all proceedings pending before Idaho courts on the effective date.