§ 19-4401.  Imposition of Tax.
   (1)   There is hereby imposed a tax on the privilege of constructing any structure for human occupancy for residential purposes, or making any improvements to any such structure, for which a building permit is required pursuant to Section A-301.1.1.
      (a)   For purposes of this Chapter 19-4400, "improvements" shall mean any repairs, constructions, or reconstruction, including additions and alterations, which have the effect of rehabilitating a structure so that it becomes habitable or attains a higher degree of housing safety, health or amenity, or is brought into compliance with the laws, ordinances, or regulations of the City of Philadelphia. Ordinary upkeep and maintenance shall not be deemed an improvement. The Office of Property Assessment, or such other agency or department designated by the Mayor, shall issue such regulations as may be necessary to clarify, in plain English, the types of construction activity that qualify as an "improvement" and the types of construction activity that do not qualify as an "improvement", as provided herein. Said regulations shall be promulgated on or before April 1, 2021.
   (2)   Fifty percent (50%) of the tax shall be payable at the time of issuance of the building permit and the remaining fifty percent (50%) shall be payable upon the issuance of a certificate of final inspection pursuant to Section A-402.5. If no certificate of final inspection is required with respect to the construction authorized by the building permit, the tax shall be paid in full at the time of issuance of the building permit.
   (3)   Exemptions. No tax required by this Chapter shall be imposed upon the following improvements:
      (a)   Improvements that are not eligible for an exemption from real estate taxes pursuant to Section 19-1303.2, 19-1303.3 or 19-1303.4, except that tax delinquency of the applicant shall not constitute ineligibility under this provision.
      (b)   Improvements that are exempt from real estate tax pursuant to Section 204 of the General County Assessment Law, 72 P.S. § 5020-204, or pursuant to the Keystone Opportunity Zone, Keystone Opportunity Expansion Zone and Keystone Opportunity Improvement Zone Act, 73 P.S. §§ 820.101 et seq.
      (c)   Improvements associated with preparing an existing residential rental unit for turn-over to a new tenant.
   (4)   Refund. The tax shall be refunded upon petition pursuant to Section 19-1703 if the improvement or construction authorized by the building permit is not actually performed and the building permit has expired or been cancelled.
   (5)   The tax shall be payable by the owner of the real estate upon which the structure is proposed to be erected or which is proposed to be improved; provided that, where the owner is a government agency, the tax shall be payable by any non-governmental owner of the proposed structure or improvement.