A Certificate of Lawfulness of Existing Use or Development (CLEUD) can have the same effect as a planning permission.

If you have built something and it has been completed for more than four years; if you have changed the use of the property to a dwelling eg by dividing a property into flats or converting an outbuilding and the use has existed for more than four years; if you have changed the use of a property or been in breach of a condition, such as an agricultural restriction for more than ten years, you may be entitled to a CLEUD without the need to apply for planning permission.

Local authorities are cautious when faced with an application, which means that you have to get it right both in terms of timing and content. When you do, it is an excellent way to enhance and maximize the value of a property.