I know there is the requirement to declare if you are carrying more than $10k when leaving Australia but what is the actual process when doing this?
You declare it on the customs departure declaration, by writing $20000 in the little box. (I am not being a smartalec, just saying it is as simple as that)
Is it simply a matter of telling immigration how much you have and the reason and then you are on your way? Or is it likely to involve more than that?
Yes it is as simple as that, and if they ask you any questions you are legally required to answer them.
We will be carrying approx $20k to return to a relative. Money was legitimately withdrawn from our bank account a few days ago so can easily be proven to be ours.
Nothing wrong with that, it is perfectly legal to carry an unlimited amount of cash with you when you travel overseas. Just in case have the internet banking on your phone ready to show the withdrawal.
I'm assuming splitting the $20k between two people won't be a good idea and would be easily picked up so that's not really an option.
Unless the declaration form implies that you are declaring as the 'group' as you do when arriving (i dont know) then splitting would be a perfectly permissable. Each person answers honestly. (but do you declare $10000 or over $10000) If you happen to be searched, and they find your money, you are legally required to answer any questions they have. There is however no reason for you to hide the fact that you are carrying $20k. In fact somewhere, in a little computer database, there is a record that you withdrew $20k of cash, and no record of where you spent it. The declaration at the airport reconciles that, nobody is going to care. If there wasnt a withdrawal, then maybe they would care a lot - sometime later.
The reason for these declarations and reporting is to catch the crooks laundering money. If you had kept this cash in a hole in the ground for 20 years, then yes it would be advisable to avoid declarations and questions, but as thats not the case you have nothing to worry about at all.
Dont take anyones word for any of this, including mine. You can find out all this information yourself on Customs or Austrac website, or you could give them a call.