Predicting the past - the problem of finding a counterfactual in Part IVA

Australia's general anti avoidance rule permits the revenue authority to strike down transactions which occurred, and the tax consequences they generated. This is the easy step. The harder task is the next step because the rule seems to require speculation about what might have happened instead, although there is currently some dispute about just how far this speculation needs to venture, and how accurately it needs to be done. Recent cases show this to be the new battleground of tax avoidance disputes the problems that inevitably arise from having to speculate about a past that did not happen, but might have.