N.Y.C. Admin. Code § 11-264: § 11-264 Tax lien; interest rate.

a. All taxes plus interest required to be paid retroactively pursuant to this part shall constitute a tax lien as of the date it is determined such taxes and interest are owed. All interest shall be calculated from the date the taxes would have been due but for the exemption, abatement or deferral claimed pursuant to this part at three per centum above the applicable rate of interest imposed by the city generally for non-payment of real property tax on such date.

b. All taxes for which payment is deferred pursuant to section 11-257 of this part shall constitute a tax lien as of the date they are due and payable in accordance with the provisions of that section.