It would appear the ATO are very particular about how payments are sent to them.
Some years ago, my uncle, a retired bank inspector, was having issue with the ATO over an assessment. The ATO eventually saw reason and reviewed the amount owing but demanded instant settlement. My uncle dutifully wrote out a cheque on a piece of toilet paper and sent it away. The ATO refused to accept the "cheque." My uncle informed them it was perfectly legal tender and they could present it to the bank. He never heard another word.