If a person or governmental unit fails to keep the records required under § 11-504 of this article, the Comptroller may: compute the sales and use tax by using a factor that the Comptroller develops by: a survey of the business of the person or governmental unit, including any available records; a survey of other persons or governmental units engaged in the same or similar business; or other means; and assess the tax due. If a person or governmental unit fails to obtain a proper resale certificate on or before the date stated in a notice of intent to assess the sales and use tax under § 11-408(b) of this article, the Comptroller may assess the sales and use tax on the sale. An assessment under this subsection is final.