The situation is that local authorities will increase the Council Tax payable on any improved property in line with the increase of its value due to the improvements.

In the old days when we paid rates rather than Council Tax, additional structures like garages and sheds etc were always evaluated as extras and charged as such. I once worked as a valuation officer and had to go out and measure any new sheds and/or garages to decide whether they warrented extra rates. So this isn't a new idea at all.

Frank L.