Property business losses

So my study text says that in a given year if I make loss on one particular property, i can either set it off against the aggregate of my property incomes from all properties i own or carry my loss forward and set it off against aggregate positive future property income. My question here is then, what if I just have one property and after making a loss in the year ending 2019/20 I decide to sell my property, so then how do i recoup my loss of the year ending 2019/20, strictly excluding any gains/losses i make on selling off the property.