Since the introduction of environmental impact assessments in 1999 it has been common practise (and a requirement for some local planning authorities) to ensure that the description of development on the planning permission contained the maximum number of uses and units.
Any change to the development that affected these uses could be amended by a Section 73 powers in the Town and Country Planning Act application. This process allowed changes to be made to a scheme as long as those changes did not result in the scale or nature of the development being substantially different from the one previously approved. It is commonly referred to as an application to vary a condition on the extant planning permission but in law creates a new permission.
A Court of Appeal decision handed down in November 2019 has now made it no longer lawful to allow S73 applications to amend the description of development. When a planning permission fixes in the description of the development the number of units or total floor space it is now no longer lawful to secure amendments via Section 73 powers, leaving developers tied to the permissions that are already in place. This makes it harder to vary planning permissions says Karen Cooksley and Colette McCormack.