Thank you for mentioning this concept as it seems to me to offer a slightly more cautious and flexible strategy than the Smith manoeuvre (i.e. focusing on paying off the mandatory debt payments and then once free of the debt, re-investing a portion or all of the original debt in a tax-deductible way). Why is this not promoted more often? It seems to carry the same inherent risk of loss as paying down the mortgage and saving for retirement in tandem, but it's more tax efficient. And there's more control over cashflow and deleveraging by paying of the mortgage first (although one must sacrifice some years of market returns). Viewed this way, any mortgage interest paid is just a drag on potential investment returns.