Tax office works on the purpose of the funds, not depending on if it was borrowed against an investment property or a place of residence.
If you are purchasing a place of residence, the borrowing is not tax deductible.
The only option is to sale the property, use all proceeds to purchase the place of residence borrowing as little as possible then use the equity in this property to purchase a new investment property borrowing 100% plus all fees and charges making the investment property much more tax effective.
Realistically, although I have clients wanting to do this all the time, I am personally against it. By the time you allow for the initial selling cost (2.5% for the real estate agent, sometimes 3%) and the stamp duty and fees and charges associated with the purchase of the 2 new properties, it is highly unlikely that the tax benefits would make up for the losses.
You are therefore better off keeping it as an investment property, you will get taxed on the income generated but I would rather be positively geared than negatively geared any days.
That is the beauty of the offset accounts where you can offset your mortgage to reduce interest payments but retain the capacity to draw down all the funds at your convenience.
pm me if you want to discuss further (got some great rates too



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