Ind. Code § 13-20-21-8

Sec. 8. Solid waste annual operation fees begin accruing January 1 of each year. The department shall assess the fees not later than January 15 of that year. A person must remit solid waste annual operation fees or an installment established under IC 13-16-2 to the department not more than thirty (30) days after the date the fees are assessed or on the date the installment is due.