A. If authorization is granted by the Commission, the applicant shall keep accurate records of the actual costs of the water system, the sewerage system, or both, and shall keep an accurate account of the revenues received and expenses incurred in connection with the operation of the system.
B. The records shall be kept in accordance with the "Uniform System of Accounts for Water Utilities" or the "Uniform System of Accounts for Sewerage Utilities", as amended, which are subject to modification by the Commission.
C. Copies of the accounting systems referred to in §B of this regulation can be purchased from the National Association of Regulatory Utility Commissioners, 1102 Interstate Commerce Commission Building, Washington, D.C. 20044.
D. For the purpose of applying the appropriate systems of accounts, water and sewage disposal companies are divided into the following four classes:
(1) Class A-----Annual utility operating revenues of $500,000 or more;
(2) Class B-----Annual utility operating revenues of $250,000 or more but less than $500,000;
(3) Class C-----Annual utility operating revenues of $50,000 or more but less than $250,000; or
(4) Class D-----Annual utility operating revenues of less than $50,000.