Without formal hearing or notice to the Attorney General the State Corporation Commission shall have the authority of its own motion to correct assessments; correct the names, addresses and gross receipts of telecommunications companies certified to the Department of Taxation pursuant to § 58.1-400.1 for eighteen months from the date of the certification; or certify to the Comptroller directing refund in any case in which there has been an erroneous assessment or erroneous payment involving or resulting from mere clerical error on the part of the Commission made in copying or typing or in arithmetic. No refund shall be ordered under the authority conferred by this section more than two years after the date of the erroneous payment.