Breaches of planning control consisting of operational development, such as building and engineering works or changing the use of a building to a dwelling, were always subject to a four-year enforcement time period. So if formal action was not taken by a planning authority against a breach of planning permission within that time, the breach would become immune from enforcement and effectively become legal.
For operational development, the 10-year clock will start to run from the date that the operations were “substantially completed” For changes of use of a building to a dwelling, the 10-year period will start from the date of the breach. However, the old four-year limit will continue to apply where operations in breach of planning were mostly completed before April 25, 2024, or where someone changed the use of a building to a dwelling without permission before April 25, 2024.