N.Y. Comp. Codes R. & Regs. tit. 16, § 461.1 – Classification of utilities.

(a) For the purpose of applying the system of accounts prescribed herein, utilities are divided into two classes as follows:
Class A. Utilities having annual steam operating revenues of $750,000 or more. Such utilities shall keep all the accounts prescribed herein which are applicable to their operations.
Class B. Utilities having annual steam operating revenues of more than $100,000 but less than $750,000. Such utilities shall keep all the accounts prescribed herein which are applicable to their operations, except those operation and maintenance accounts in which the letter B does not appear in the prefix.
(b) The class to which any utility belongs shall be determined by the average of its annual steam operating revenues for the three years next preceding the effective date of this system of accounts. If at the end of any calendar year following the effective date of this system of accounts the annual steam operating revenues of the utility for the three years ended on that date shall average $750,000, then such utility shall be classified as a class A utility for the next succeeding year.
(c) Any utility may at its option adopt the system of accounts prescribed herein for class A utilities. Notice of such action shall be promptly filed with the commission.