To register for the site, (https://onlineservices.ato.gov.au), you will need your tax file number, as well as additional private information known to only you and the ATO. You will also need to choose a secure password.
On the website, you can manage your tax including checking the progress of your tax return and viewing your income tax account balance, checking the balance of your super account and transferring or consolidating your super into a fund of your choice.
The site also contains links to handy tools, like a calculator that checks whether the correct amount of tax is being withheld from your pay. If you have a tax debt, you can also enter into a repayment arrangement with the ATO on the site.
So give it a go today and take back some control of your tax.