N.Y.C. Admin. Code § 11-2103: § 11-2103 Presumptions and burden of proof.

For the purpose of the proper administration of this chapter and to prevent evasion of the tax hereby imposed, it shall be presumed that all deeds and transfers of economic interests in real property are taxable. Where the consideration includes property other than money, it shall be presumed that the consideration is the value of the real property or interest therein. Such presumption shall prevail until the contrary is established and the burden of proving the contrary shall be on the taxpayer. The burden of proving that a lien or encumbrance existed on the real property or interest therein before the delivery of the deed and remained thereon thereafter and the burden of proving the amount of such lien or encumbrance at the time of the delivery of the deed shall be on the taxpayer.