Various tax matters.

Removes references to an out-of-state merchant's collection of the state use tax. (Under current law, an out-of-state merchant is required to collect the state gross retail tax (not the use tax) on retail transactions made in Indiana if certain threshold conditions are met.) Makes clarifying and technical changes to the definitions of "bundled transaction", "unitary transaction", and "gross retail income" in the sales tax statute, and "adjusted gross receipts" in the sports wagering statute. Removes outdated references to the gross income tax and adjusted gross income tax. Makes a technical correction in the gasoline use tax statute. Changes the definition of "Internal Revenue Code" in the adjusted gross income tax law to mean the Internal Revenue Code of 1986 as amended and in effect on January 1, 2020. Clarifies the allowable state income tax deductions and credits for a married individual filing a separate return. Requires a payor of prize money to an initial recipient in connection with a racing event at a qualified motorsports facility to withhold adjusted gross income tax from the payment of the prize money. Provides that a taxpayer is entitled to claim a historic rehabilitation tax credit granted for a year other than the year in which the preservation or rehabilitation of the historic property was performed and certification provided, notwithstanding the expiration of the historic rehabilitation tax credit chapter on January 1, 2019, and the cap on the amount of credits allowed in a state fiscal year beginning after June 30, 2016. Defines "loans arising in factoring" under the financial institutions tax statute. Specifies the duties of the motor carrier service division of the department of state revenue (department). Removes obsolete provisions related to transporting gasoline or special fuel. Eliminates a redundant penalty provision for failure to file a quarterly motor carrier fuel tax report (this penalty is currently assessed and calculated under the penalty provisions of the International Fuel Tax Agreement as set forth in another section of the Indiana Code). Authorizes the department to require a taxpayer to execute a power of attorney for representation of the taxpayer on a form prescribed by the department. Requires each county to periodically submit certain data to the GIS officer. Allows a taxpayer to request a secondary review of adjustments to tax attributes in certain circumstances. Makes clarifying changes to the statute of limitations for tax assessments and tax refunds. Extends the statute of limitations for assessments for certain partners and partnerships. Allows for certain disclosures of a taxpayer's information concerning returns and remittances for a listed tax in connection with the department's online tax system to an individual without a power of attorney. Provides that after a date determined by the department, not later than September 1, 2023, the department may not make disclosures of a taxpayer's information concerning returns and remittances for a listed tax to an individual unless the individual has a power of attorney or is otherwise authorized to receive the information by law. Extends the statute of limitations to allow a refund of state and local income tax with regard to veterans' disability severance payments that were determined to qualify for a refund of federal income tax under the Combat-Injured Veterans Tax Fairness Act of 2016. Revises the penalty provisions related to payments made to the department by a payment instrument on which the department is unable to obtain payment. Expands the functions of the taxpayer rights advocate office within the department. Repeals the state revenue pilot program fund. Provides that any money in the state revenue pilot program fund before its repeal is transferred to the motor carrier regulation fund. Makes conforming changes.