Dear Luke
The key issue is your business structure. If you operate as a sole trader or partnership in Australia, then you would be subject to Australian tax. The same applies if you have an Australian registered company.
However, if you set up a company overseas, say in the US, you will pay company tax there. You will pay tax in Australia on dividends paid to you by the US company (if you set one up), but only if you are an Australian resident.
I don't think you would would be considered an Australian resident for tax purposes, if you are travelling overseas for a few years.
I agree with the advice form the other posts that you need to talk to an accountant. I would also suggest you have a look at the ATO website which has a section entitled "International Tax Essentials"
http://www.ato.gov.au/individuals/pa...58#001_002_012
I hope that helps.
Michael Terceiro
Solo Lawyer
www.terceiro.com.au