IDK i actually did this so i could get help with a debate. I think it will cause overpopulation problems from having kids or something like that. So i think that this will do that by causing people to have kids so they can get some of their tax payer money back, which not only does it cause problems, but ensures that the wuality of the kid would be worse
You may try to spin this as giving back to non-parents, but it is really taxing parents more when they have kids, since they would have had the rebate before hand, and now no longer have access to it, and since if it is simply a cut in taxes, then that means that there will be fewer services such as schools, roads, and hospitals.
As for taking money away from parents, I think that this is terrible, since now, not only does the parent have to feed extra mouths to feed, now they must pay the government extra. This would make it more difficult to successfully nourish and educate their children, especially with cuts to other government services, resulting with a lower quality next generation.
This, alongside a sudden drop in parentage due to a change in incentives, would cause the Australia of tomorrow to have fewer people, of whom fewer would be highly productive. This would damage the Australian economy long-term, contributing to increase in suffering, not just in the short-term, but the long-term as well.
Finally in terms of overpopulation, Australia is in no danger. Australia today has fewer people than was in the UK alone in 1900, and yet it has over 30 times the land area. Even considering that large areas of Australia is desert, Australia still has nearly 8 times the arable land area of the UK. All with a population lower than the UK population over 100 years ago.
To conclude, this policy would cause great damage to Australia, both now and in the future, all to prevent a problem that does not exist in terms of Australia.