Do I have to live in it to be exempt from tax?

If I bought a plot of land and built a house, would I pay tax if I sold it and used all the sale proceeds to purchase another property or land, or would I have to live in it firstly as my principal private residence (PPR)? If I move in, how long do I have to live there for exemption?

If you sell the house without living in it - yes, you will be liable to tax. If you live in it before you sell it - you can make it into your PPR. There is no fixed answer to how long you need to live in it to make it your PPR. You need to be able to demonstrate that you moved in with the intention to stay long term. Some tax advisers would say you need to live in it for at least between six months and a year.