SB 243: Various tax matters.

Amends and adds state income tax statutes to conform with certain provisions enacted in Public Law 119-21 (H.R. 1) (commonly known as One Big Beautiful Bill Act of 2025). Specifies rounding provisions for cash transactions with regard to the penny phaseout. Amends state income tax withholding provisions for gambling winnings. Amends the definition of "contribution" for purpose of the state income tax credit for contributions to an ABLE account. Amends provisions regarding computation of specified research or experimental expenditures. Authorizes the department of state revenue (department) to mail documents electronically through its online tax system. Allows taxpayers to request to receive all documents from the department through the department's online tax system. Makes changes to certain tax warrant procedures. Extends the deadline for filing revenue agent report (RAR) adjustments from 180 days to one year from the Internal Revenue Service's finalization of the federal adjustments. Amends the statute of limitations for issuing assessments and refunds based on an RAR to one year. Adds certain sales tax enforcement provisions regarding motor vehicles, cargo trailers, aircraft, and watercraft. Amends provisions regarding confidentiality of tax information. Makes various changes to the cigarette tax chapter, the petroleum severance tax chapter, and the alcoholic beverage excise tax chapters. Specifies the liability of responsible persons for trust fund taxes. Defines the term "responsible person" with regard to trust fund taxes. Specifies application of the Indiana adoption tax credit. Revises provisions in the pass through entity tax regrading credit for taxes paid to another state. Amends provisions in the tax amnesty program. Specifies the determination of estimated tax penalties. Makes amending changes to the aircraft license excise tax.