High-income luxury deregulation was added to the Rent Stabilization Law (RSL) pursuant to the Rent Regulation Reform Act of 1993. RSL §26-504.3(a)(1) addresses the issue of whose income is to be counted:

Total annual income means the sum of the annual incomes of all persons who occupy the housing accommodation as their primary residence other than on a temporary basis, excluding bona fide employees of such occupants residing therein in connection with such employment and excluding bona fide subtenants in occupancy pursuant to the provisions of section two hundred twenty-six-b of the real property law.

Although the statute talks about counting the income of household occupants, it does not specify the date that is to be used to determine who lives in an apartment for purposes of luxury deregulation.