Probably not much help … but for the record, My (Our) Trading account is registered with both mine and my wife’s names on it ……. (about 10+ years now)
Whatever profit or loss is registered on that trading account for the year is simply divided by two and added to our respective personal tax returns … along with any allowable deductions of course (eg. my 2016 porche, my 10 screen computer and all overseas holidays …. all divided by two)
I have neglected for the last 2 years to tell my wife that I claim my 9 foot tinny on my tax return only. I am a bad man I know
As for a formalised Partnership with a separate ABN and TFN … my guess would be either one of two scenarios …
1) The tax return for the partnership account would need to be assessed first, then the „resulting“ profit/loss simply added to your individual returns …. or
2) More likely, the partnership account is now a separate entity and any resulting profit/loss/tax liabilities are only registered on that tax return .. ie. any profit/loss is not duplicated on your personal returns, therefore no possible double taxing problems.
All my jibbering above aside …. I think a 5 minute chat to a decent accountant would set you straight … and I am definitely not a decent accountant
Good luck and keep us all posted