Had a the same problem Eagle
When I live in Sydney the govermaent put $4000 in our account , they stuff up the child allowance.
When I rang them they said no its all good then two week later they send me a rude letter saying I owe them $4000 they did get wrong.
Then I got my rebate back on the Pink Batts project and then a month later they pay me againe I rang them and told them and sent the money back.
Just makes you wonder how much they give away every year and not pick up on it
Cheers
Strucky