No. Certain developments can be done without the need for planning permission. This is known as “permitted development”. However, some or even all permitted development rights can be withdrawn by the use of an “Article 4 Direction”. This is issued when specific control is required over-development in an area of special importance, such as a conservation area.
A given size of extension is usually permitted development, which is normally set in cubic metres and percentage of the original building. However, any work undertaken on the property since its construction counts towards this volume, including any work done prior to you moving in. You should seek advice from Norton Taylor Nunn before considering undertaking additional work, just to be sure.
For further guidance on when is permission required, visit the government website which sets out when planning permission is required and different types of planning permission which may be granted.