It is a requirement for every local planning authority in Wales to undertake a Joint Housing Land Availability Study (JHLAS) on an annual basis in order to monitor the supply of land that is available for housing in their areas.

Planning Policy Wales states that local planning authorities have to ensure that sufficient land is available, or will become available, to ensure a five year land supply for housing.

Technical Advice Note (TAN) 1, 'Joint Housing Land Availability Studies' by the Welsh Government, provides guidance for calculating the available housing land supply.