True it's up to the individual how they want to go about it. The thing is this isn't some loophole that you would exploit, it appears to be written on the ATO website itself. So it seems to be as standard as claiming deductions and expenses. As long as you go through a tax agent at least for the first BAS and GST credit claim, then you can double check with them and be rest assured you are doing it within the regulations, and are less likely to be audited. I vaguely remember one person on a forum saying they had been claiming the GST credit for years and hadn't been audited, but don't know how much you can believe on general forums.
When I was making more money before, the ATO asked me to complete BAS quarterly even though I didn't have an ABN. If they ask me to do BAS again then I would definitely register an ABN and do this GST credit thing, because I would already be filling out the forms anyway. For me personally I think over $200 and I'd claim ($50 per quarter), because it's super quick to work out the totals in excel and then the BAS is just two pages. It seems so little when I definitely lose multiples of that on a bad trade but it's also about half an hour of work to get $50.
