Indiana Code Title 6. Taxation § 6-7-2-0.1

(1) “actual cost” means the price paid by a remote seller for an individual taxable product;  and

(2) “actual cost list” means an annual list (prepared, maintained, and certified by each remote seller) of the cost of each individual taxable product.  For purposes of this subdivision, the actual cost for each individual product in a cost list shall be the average of the actual price paid by a remote seller for the individual product over the twelve (12) calendar months prior to January 1 of the year in which the sale by the remote seller occurs.