I will shortly have a lump sum which I would like to pay off my mortgage.I have a mortgage on my PPR & also on an investment property.All things being equal I would of course pay the lump sum off my PPR. My PPR is on tracker of .5 above ECB wheras my investment rate is 4.05%. If I were to pay off on the investment mortgage would I have a reasonable case with revenue to claim the interest on the same portion of my PPR loan interest in lieu? This would mean I would be claiming less interest overall and of course mean I would be paying more tax to the revenue. I do already claim a portion of interest on my PPR as it I topped it up to fund site purchase for investment property. Maybe after December this will be purely academic if interest relief on investment mortgages is abolished!!! I'l surely be in trouble then.