Since I am only of the very few Australian residents I know who haven’t had an employer stuff up their tax withholding, a useful link: the ATO tax withheld calculator for PAYG employees.
It’s in the ‘for employers’ part of the ATO site, but employees can use this to check whether each pay packet they receive has had the correct amount of tax taken out. It doesn’t rule out the possibility of tax refunds or debts because it doesn’t take into account a mountain of stuff, the major one being non-employment income but also private health insurance stuff, deductions, blah blah. But it does mean you can catch the most common payroll mistakes, the big one being an employer forgetting to take out a HELP payment. If a payroll mistake results in you having a tax debt, you’re just as liable for it as in any other circumstances (assuming that the extra money turned up in your pay, which is what a mistake usually means) so unfortunately it is a good idea to double check that your after-tax amounts match the tax table whenever you get a new job or a pay rise.