15-70-715. Penalties for refusal or failure to file return or pay tax when due. (1) If a compressed natural gas dealer or a liquefied petroleum gas dealer refuses or fails to file a return required by this part within the time prescribed by 15-70-103 and 15-70-714, there is imposed a penalty of $25 or a sum equal to 10% of the tax due, whichever is greater, together with interest at the rate of 1% on the tax due for each calendar month or fraction of a month during which the refusal or failure continues. If a compressed natural gas dealer or a liquefied petroleum gas dealer establishes to the satisfaction of the department that the failure to file a return within the time prescribed was due to reasonable cause, the department shall waive the penalty imposed by this section.

(2) Whenever a compressed natural gas dealer or a liquefied petroleum gas dealer files a return but fails to pay in whole or in part the tax due under this part, there must be added to the unpaid amount due interest at the rate of 1% a month or fraction of a month from the date on which the tax was due to the date of payment in full.