New York Codes, Rules and Regulations
Title 20 - DEPARTMENT OF TAXATION AND FINANCE
Chapter I - Franchise and Certain Business Taxes
Subchapter F - Tax On The Furnishing Of Utility Services
Part 47 - Records
Section 47.2 - Methods of accounting

(a) The State Tax Commission is not disposed to put utilities to the additional expense of establishing new or revised accounting systems or of keeping additional or supplemental records. It will consider adequate and satisfactory the accounting methods--cash or accrual--regularly employed by the taxpayer, if the accounts so kept admit of the computation of gross income, or gross operating income as the case may be.

(b) Satisfactory explanations will be required concerning any changes in regular methods of keeping accounts.