Tax Law, § 1145(a)(1)(vi)
In determining whether there is substantial authority (other than in cases described in paragraph [4] of this subdivision), only the following will be considered authority: applicable provisions of the Tax Law and other statutory provisions; regulations of the Commissioner of Taxation and Finance and regulations proposed by the Commissioner of Taxation and Finance construing such law; court cases; administrative pronouncements (including technical memoranda); Tax Department and other official explanation of such law and regulations; and legislative intent as reflected in bill memoranda. Conclusions reached in treatises, legal periodicals, legal opinions or opinions rendered by other tax professionals, and descriptions of statutes prepared after enactment are not authority. The authorities underlying such expressions of opinion, where applicable to the facts of a particular case, however, may give rise to substantial authority for the tax treatment of an item.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 536.2