Pat, in saying that there is no gaurantee that your lay bet will be matched, there is also no gaurantee that the individual spread betting will be profitable either. It's the fact that if you demonstrate to continually be matched over a period of time at a profitable margin in high dollar amounts that would determine whether your at the skill/commercial or chance/recreational end of the spectrum.

However I agree that its highly unlikely anyone would have to pay tax but at the same time UB has a point that there really isn't much stopping the ATO targetting someone making a living via sports/racing trading.