Indiana Code Title 36. Local Government § 36-7-4-1319

Sec. 1319. (a) A unit shall amend a zone improvement plan to make adjustments in the nature, location, and cost of infrastructure and the timing or sequencing of infrastructure installations to respond to the nature and location of development occurring in the impact zone.  Appropriate planning and analysis shall be carried out before an amendment is made to a zone improvement plan.

(b) A unit may not amend an impact fee ordinance if the amendment makes a significant change in an impact fee schedule or formula or if the amendment designates an impact zone or alters the boundary of a zone, unless a new or substantially updated zone improvement plan has been approved within the immediately preceding one (1) year period.