Following up finally on comments that bigchrisb made about paying off the mortgage faster and then redrawing the money to investment in shares/refinance margin loans. This appears to be the ATO ruling on this. So, there is no problem to do this, but I have been thinking about the practicalities. It seems to me that if you pay off say $50k of the mortgage and then withdraw the money for investment, then the next $50k you pay off just repays the redraw and so your tax deductible loan gets no bigger. So, it only makes sense then to do the redraw after paying off as much of the mortgage as you want in the long term before doing the investment loan. So, in the meantime I think we will continue to accumulate money in the offset account, which gives more flexibility. If you are wondering why we should pile up cash while having a margin loan, actually the effective untaxed interest on the offset account is higher than the after tax rate on the margin loan. So, it makes sense to borrow more on the margin loan while piling money up in the offset. I think I will stop automatic re-investments of distributions and dividends where there is no discount for re-investment to speed the process a little. The only one I think is with my Colonial First State funds. When we are nearer an amount I think is reasonable then it would make sense to actually sell investments and add that money to the pile. But that should be a final step I think. I do have a lot of tax losses so that the first $60k of capital gains is tax free. This will be a project over several years. Of course, maybe in the end we would take the cash pile and use it as a downpayment on an investment property instead :) So, lots of things are possible.
For U.S. readers who might wonder about why go through this complicated plan.... in Australia, mortgage interest is not tax deductible for owner occupiers. But investment interest is, even if it exceeds the income on the investment so that you make a net loss. The latter is known as "negative gearing".
From March on, I'll include the implicit saved mortgage interest as part of investment return. That means that it also needs to be included in the "transfer from current account to housing" and included in housing expenses in the account in order to balance all the books. I'll also include the "core housing expenditure" in the accounts which will be the actual interest paid to the bank.