One,

The credit note is just one of many instruments that is used in a multitude of ways that can completely bypass any FET, just remember that:
1 - Australia cannot legislate against overseas transactions.
2 - Tax avoidance is entirely legal. Evasion is not.

Credit notes like hundreds of financial instruments have 100 000s of transactions every day mostly internal, in order to plug the many leaks in the tax, the FET would have to become so complex and intrusive that the cost of compliance and enforcement would outweigh its returns.

This tax and similar ones have been talked about for many decades, but no one has been silly enough to impose one.

Maybe you have a point SM. I'm no expert in financial transactions which is why my original post ended with "Could this be implemented?"

I do however still think that there must be non-complex method of taxing money that leaves the country.

Not one that works.

Yet ...

:-)