I wasn't sure where to put this... mods, please move if desired.

I'm hoping that with such a diverse membership someone may have some experience/advice...or know someone who has had similar... thanks in advance if so.

I lived in Perth WA for a couple of years before moving to Thailand, and during that time bought an apartment during the so-called rejuvenation of inner city Perth.

This apartment has been let through an agency since 2013, and... well... I don't seem to have declared any income. It's been a busy few years, I've been distracted, etc etc, but all said and done I didn't address the issue to start with and time slipped by... and now have six undeclared tax years, and well on my way to the seventh.

Recently this has started playing on my mind, and with my daughter's future very important to me I'm wanting to sort this out and become legal. One day I may come to sell the apartment and I'm sure with the capital gains I'll be liable to, the tax authorities may well dig a bit deeper. And to be honest, I just want this off my mind.

Just some details... I'm a British citizen and have never been in the Australian tax system. I have no tax history, no tax id and have never worked in Australia. I think it would be extremely unlikely I'd ever go back to live there, but occasional visits would be nice. My daughter has tri-citizenship, including Aussie. I think an apartment in East Perth may well be useful to her in the future, maybe for accommodation during further education if she goes that way.

I've just spent a morning organising nearly 7 years worth of rental statements and End of Year Statements provided by the letting agents in Perth, but what's the next step?

Does anyone have experience of this? Are the Australian tax authorities likely to catch up with me?
Is there such a thing as an amnesty if I approach them and come clean? What kind of penalties could I expect on top of what I assume wold be huge interest charges.

My rough plan now is to approach Australian accountants and put this to them, and see what they suggests. I don't just want to needlessly waste money though, as I'm sure the wrong accountancy firm could spend hours over this and fleece me.

Any advice please?