N.Y. Comp. Codes R. & Regs. tit. 20, § 528.1 – General.

(a) The Tax Law provides for exemptions from the sales and compensating use tax of receipts from the sale, or use of certain types of property and services, and certain usages of property and services. These exemptions are covered in the following sections of this Part.
Cross-reference:
Exemptions of certain admissions, see section 527.6 of this Title. Exemptions from compensating use tax, see section 531.5 of this Title.
(b) The Tax Law provides for exemption from the sales and compensating use tax of transactions with certain entities and organizations. (See Part 529 of this Title.)
(c) Exemptions from the sales and compensating use tax are strictly construed. For an exemption to be allowed, it must clearly appear that a transaction is eligible for the exemption. The burden of proving nontaxability is on the person claiming the exemption.