Indiana Code Title 6. Taxation § 6-6-1.1-904.1

Sec. 904.1. (a) To claim a refund under section 902, 902.5, or 903, of this chapter, a person must present to the administrator a statement that contains a written verification that it is made under penalties of perjury and that sets forth the total amount of gasoline purchased and used for purposes other than propelling a motor vehicle on an Indiana public highway.  The statement must be filed by April 15 of the year succeeding three (3) years after the date the gasoline was purchased, and it must be accompanied by the original invoice or a certified copy of the original invoice.  Such a copy must be certified by the supplier on forms prescribed by the administrator.  In addition, the original invoice or certified copy must show either:

(b) The administrator may make any investigations the administrator considers necessary before refunding the gasoline taxes to the consumer.