When the commissioner has reason to believe that a hospital has failed to file a return or to include any part of its net patient services revenue in a filed return, the commissioner may require the hospital to file a return or a supplementary return showing such additional information as the commissioner prescribes. Upon the receipt of the supplementary return, or if none is received within the time set by the commissioner, the commissioner may find and assess the amount due upon the information that is available. The making of such additional return does not relieve the hospital of any penalty for failure to make a correct original return or relieve it from liability for interest imposed under N.H. Rev. Stat. § 21-J:28 or any other additional charges imposed by the commissioner. This section shall not be construed to modify the statute of limitations provided in N.H. Rev. Stat. § 21-J:29.