What is the 'Vacant Building Credit' in respect of affordable housing contributions?

All applications for 15 or more (net) residential units are required to make a contribution to affordable housing equivalent to 40% of the new housing in accordance with the Local Plan. This is done through the provision of dwellings on site, or in exceptional circumstances through financial or other contributions. In any case the amount to be provided will, from 1 December, now have deducted from that calculated provision a 'credit' equivalent to the gross internal floorspace of any existing vacant building brought back into use or demolished as part of the scheme.