If somebody buys two adjoining houses and wants to knock them into one, do they need planning permission, approval from the council, and would they still have to pay council tax on both properties?
I know someone who did this - single mum & single dad in adjoining properties got together & decided to make it a single home for their enlarged family. I don't think there were any issues regarding planning but they had a helluva job getting the council to accept it as one property for council tax.
Depends whether the area is classed as a conservation area and how historically sensitive the building is, regarding planning. Any physical works to the structure will require building regulations approval.
In this case, Planning rules are concerned with what is known as "class use".
Residential being one class. Business use is another class. To convert two houses to one does not involve a change of use. It's the same reason why converting your garage usually needs no Planning consent.
There are exceptions of course. Conservation Areas may affect this. So would Listed Building status. There could be others to consider.
A planning permission is sometimes required to join two different houses into one. The rules vary in different places. A planning permission is not required for doing any internal works, in case of doing any external changes then you may require a planning permission.