Answer
Do I need planning permission for a hot tub?
The hot tub itself, no; a raised deck or enclosure around it can.
In short
A hot tub itself is not a building, so it needs no planning permission. What can need it is a structure around it, such as a raised deck above 0.3 metres or an enclosure, which follows the decking and outbuilding rules, and any privacy screening over 2 metres.
A note
General guidance, not advice. Rules vary by site, and Article 4 directions or conditions can change what applies. Check with your local authority and the Planning Portal.
Arrange a consultation
Send a few photographs and a sentence about the site. We will reply personally.