One of the first things that you MUST do on entering Australia as a migrant is to apply for a tax file number. Without this number you can work, but you will pay more tax!!! Your Tax File Number is much the same as your National Insurance number in the UK
The Australian Taxation Office is the place to go to get your tax file number which takes around 4 weeks to arrive, but can arrive earlier if you are lucky!
If you start a job before you receive your tax file number that’s fine. However, if you get paid by your employer before you get the number then you will be taxed at an emergency rate which is far higher than you would pay if you have the tax file number
This Fact Sheet has everything you need to know about getting and using your tax file number