(7) Notwithstanding any other provisions of law, when a head of a household to whom a then current, valid rent exemption order has been issued under this chapter, chapter three or chapter seven of this title moves his or her principal residence to a subsequent dwelling unit subject to regulation under this chapter, the head of the household may apply to the department of finance or such other agency as the mayor shall designate for a rent exemption order relating to the subsequent dwelling unit, and such order may provide that the head of the household shall be exempt from paying that portion of the legal regulated rent for the subsequent dwelling unit which is the least of the following:
(i) the amount by which the rent for the subsequent dwelling unit exceeds the last rent, as reduced, which the head of the household was required to actually pay in the original dwelling unit;
(ii) the last amount deducted from the maximum rent or legal regulated rent meaning the most recent monthly deduction for the applicant in the original dwelling unit pursuant to this section or section 26-605 of this title; or
(iii) where the head of the household does not receive a monthly allowance for shelter pursuant to the social services law, the amount by which the legal regulated rent of the subsequent dwelling unit exceeds one-third of the combined income of all members of the household except that this subparagraph shall not apply to any eligible head of the household who has been granted a rent increase exemption order that is in effect as of January first, two thousand fifteen or takes effect on or before July first, two thousand fifteen.