24 C.F.R. § 983.52
(a) Ineligible unit. A HAP contract must not be effective and no PBV assistance may be provided for any of the following:
(d) Prohibition against assistance for units for which commencement of construction or rehabilitation occurred in violation of program requirements. Unless a PHA has exercised the discretion at § 983.154(f), to undertake development activity without an Agreement or to execute an Agreement after construction or rehabilitation that complied with applicable requirements of § 983.153 has commenced, or at § 983.157, to undertake development activity after execution of the HAP contract, the PHA may not execute a HAP contract for units on which construction or rehabilitation commenced after the date of proposal submission (for housing subject to competitive selection) or the date of the PHA's board resolution approving the project-basing of assistance at the project (for housing excepted from competitive selection) and prior to the effective date of an Agreement. At HUD's sole discretion, HUD may approve a PHA's request for an exception to this prohibition. In determining whether to approve the PHA request, HUD will consider appropriate factors, including the nature and extent of the construction or rehabilitation that has commenced.