N.Y. Comp. Codes R. & Regs. tit. 16, § 561.2 – Records.

(a) Each utility shall keep its books of account and all other books, records, and memoranda which support the entries in such books of account so as to be able to furnish readily full information as to any item included in any account. Each entry shall be supported by such detailed information as will permit ready identification, analysis, and verification of all facts relevant thereto.
(b) The books and records referred to herein include not only accounting records in a limited technical sense, but all other records, such as minute books, stock books, reports, correspondence, memoranda, etc., which may be useful in developing the history of or facts regarding any transaction. All such records shall be accessible, at all times, to the authorized representatives of the commission at a location within the State of New York, unless the company is specifically exempted by order of this commission.
(c) No utility shall destroy any such books or records unless the destruction thereof is permitted by rules and regulations of the commission.
(d) In addition to prescribed accounts, clearing accounts, temporary or experimental accounts, and subdivisions of any account, may be kept, provided the integrity of the prescribed accounts is not impaired.
(e) All amounts included in the accounts prescribed herein for water plant and operating expenses shall be just and reasonable and any payments or accruals by the utility in excess of just and reasonable charges shall be included in account 426, Miscellaneous Income Deductions.
(f) The arrangement or sequence of the accounts prescribed herein shall not be controlling as to the arrangement or sequence in report forms which may be prescribed by the commission.
(g) Not later than March 31, 1974, each utility shall have filed with the commission a copy of its manual of accounts, or other systematic statement of accounts showing every account or subaccount kept during the year 1973, and thereafter shall file (either as changes occur, or for each calendar year at a date not later than the filing of its annual report) a statement of each account, subaccount, and clearing account opened or discontinued and the effective date of such change. For each clearing account opened, the purpose of the account shall be stated.