Will we pay higher stamp duty on a buy-to-let property?

My partner and I already own homes, but want to purchase another to help our children later on Q My partner and I - we are not married - live in his house, which he owns outright in his sole name. I also have a house in my name only. There is a mortgage on this property, which will be rented out once it has been renovated. We are thinking about jointly buying another buy-to-let house but won't need a mortgage to do that. The property we are looking at will cost £220,000. Will we have to pay ext...