65863. (a) Each city, county, or city and county shall ensure that its housing element inventory described in paragraph (3) of subdivision (a) of Section 65583 or its housing element program to make sites available pursuant to paragraph (1) of subdivision (c) of Section 65583 can accommodate, at all times throughout the planning period, its remaining unmet share of the regional housing need allocated pursuant to Section 65584, except as provided in paragraph (2) of subdivision (c). At no time, except as provided in paragraph (2) of subdivision (c), shall a city, county, or city and county by administrative, quasi-judicial, legislative, or other action permit or cause its inventory of sites identified in the housing element to be insufficient to meet its remaining unmet share of the regional housing need for lower and moderate-income households.

(b) (1) No city, county, or city and county shall, by administrative, quasi-judicial, legislative, or other action, reduce, or require or permit the reduction of, the residential density for any parcel to, or allow development of any parcel at, a lower residential density, as defined in paragraphs (1) and (2) of subdivision (g), unless the city, county, or city and county makes written findings supported by substantial evidence of both of the following:

(A) The reduction is consistent with the adopted general plan, including the housing element.

(B) The remaining sites identified in the housing element are adequate to meet the requirements of Section 65583.2 and to accommodate the jurisdiction's share of the regional housing need pursuant to Section 65584. The finding shall include a quantification of the remaining unmet need for the jurisdiction's share of the regional housing need at each income level and the remaining capacity of sites identified in the housing element to accommodate that need by income level.

(2) If a city, county, or city and county, by administrative, quasi-judicial, legislative, or other action, allows development of any parcel with fewer units by income category than identified in the jurisdiction's housing element for that parcel, the city, county, or city and county shall make a written finding supported by substantial evidence as to whether or not remaining sites identified in the housing element are adequate to meet the requirements of Section 65583.2 and to accommodate the jurisdiction's share of the regional housing need pursuant to Section 65584. The finding shall include a quantification of the remaining unmet need for the jurisdiction's share of the regional housing need at each income level and the remaining capacity of sites identified in the housing element to accommodate that need by income level.

(c) (1) If a reduction in residential density for any parcel would result in the remaining sites in the housing element not being adequate to meet the requirements of Section 65583.2 and to accommodate the jurisdiction's share of the regional housing need pursuant to Section 65584, the jurisdiction may reduce the density on that parcel if it identifies sufficient additional, adequate, and available sites with an equal or greater residential density in the jurisdiction so that there is no net loss of residential unit capacity.

(2) If the approval of a development project results in fewer units by income category than identified in the jurisdiction's housing element for that parcel and the jurisdiction does not find that the remaining sites in the housing element are adequate to accommodate the jurisdiction's share of the regional housing need by income level, the jurisdiction shall within 180 days identify and make available additional adequate sites to accommodate the jurisdiction's share of the regional housing need by income level. Nothing in this section shall authorize a city, county, or city and county to disapprove a housing development project on the basis that approval of the housing project would require compliance with this paragraph.

(d) The requirements of this section shall be in addition to any other law that may restrict or limit the reduction of residential density.

(e) This section requires that a city, county, or city and county be solely responsible for compliance with this section, unless a project applicant requests in his or her initial application, as submitted, a density that would result in the remaining sites in the housing element not being adequate to accommodate the jurisdiction's share of the regional housing need pursuant to Section 65584. In that case, the city, county, or city and county may require the project applicant to comply with this section. The submission of an application for purposes of this subdivision does not depend on the application being deemed complete or being accepted by the city, county, or city and county.

(f) This section shall not be construed to apply to parcels that, prior to January 1, 2003, were either (1) subject to a development agreement, or (2) parcels for which an application for a subdivision map had been submitted.

(g) (1) If the local jurisdiction has adopted a housing element for the current planning period that is in substantial compliance with Article 10.6 (commencing with Section 655