Probably one for the likes of Forces Sweetheart here so.... If I had the means should I pay off the interest only mortgage on my rented out house and thereafter pay tax on all of the profit as opposed to using the interest charges to reduce my tax bill? OR Should I keep the mortgage and pay the cash that I would have used to clear the mortgage into cash and share mini ISAs in the hope that this will be more tax effiecient? Despite many hours of trying I can't get my head around the numbers? Can anyone help?