During the process, interest on your investment loans capitalizes. Capitalised interest is deductible in these circumstances providing your dominant purpose is not a tax benefit. In TD 2011/D8 the ATO states that simply wanting to pay your home loan off sooner may not prevent them finding that your dominant purpose was a tax benefit. Accordingly, we recommend you get an ATO ruling before claiming a tax deduction for the capitalized interest, we can organize this for you or you can simply do it yourself by following the instructions on http://www.bantacs.com.au/capitalising-interest.php