Indiana Code Title 4. State Offices and Administration § 4-10-23-10

Sec. 10. (a) Before the first business day in October of each year, the department of state revenue shall calculate the income tax incremental amount and the gross retail incremental amount for the preceding calendar year for the district.

(b) Businesses operating in the district shall report, in the manner and in the form prescribed by the department of state revenue, information that the department determines necessary to calculate incremental gross retail, use, and income taxes.

(c) It is the intent of this section to identify all sales, use, and income taxes of all taxpayers that are apportionable to the taxpayer's activities in the district.  This section shall be broadly construed by the department of state revenue in order to achieve the purposes of IC 5-1-17.5.