Do I need to do anything in particular to be allowed back into Australia as a permanent resident again after living overseas for 4 years? I have a valid Aussie passport.

So you are saying that you are an Australian citizen and you are moving back to Australia to live?

Exactly. Do you know where i need to go, or what i have to do to become a permanent resident again?

So long as you haven't renounced your Australian citizenship (or lost it in some other way) and your Australian passport is current, you don't need to do anything other than use your Australian passport to return to Australia, according to this page: http://www.immi.gov.au/media/fact-sheets/95documents.htm. Because you are a citizen, you have automatic right of entry to your home country :)

Thanks for that. It's cleared up a lot for me. Do you know what i must do once i get to Australia to inform of my new permanent address? Is it CenterLink? Thanks for your help. Great site.