The Australian tax system is basically an honesty box patrolled by Auditors. Unless you have a good Accountant that knows the system back to front you won't know what's legal until an auditor runs through your books. With modern banking, everything is linked and they have pretty much all your income/expenditure at their fingertips, what they will want in addition is your excuses for claiming, and or not paying tax, and then come back to you on whether it's right/wrong and how much you owe. If you are earning decent coin overseas it would be best to get proper advice from an accountant with experience in the area, as they say, negligence is not a defense, and depending on how much you owe and the auditor on the day you could be fined as well as owing tax. On the commuting aspect, is commuting paid for by the operator considered a fringe benefit and taxable? Repositioning for duty is definitely not, but commuting is a different concept in the tax world.