[mitemte]

In Australia, if you work in multiple places and at multiple companies, it’s still trivial to file your own taxes. You log in to the government portal, where the collected amounts of tax from each income source, including bank interest, is listed. It can get more complicated if you have your own business but for the majority of people it’s easy and doesn’t require a third party.

[vel0city]

Australia has a progressive tax structure, right? If you have multiple income sources how does each source know the proper withholdings? How do they know what deductions you'll be eligible for or are wanting to take?

[Skinney]

If it works anything like what we've got in Norway, they take a rough percentage, and once every year when the taxes are filed, the IRS equivalent charges or repays the missing amount.

[fn-mote]

I don't understand how these could be issues. They aren't in my country.

You're still responsible.

Tell each company how much to withhold.

If they take too much, you get it back when you file taxes.

If they don't take enough, you pay a penalty for having too large of a bill when you file.

The issues you mention exist regardless of how many employers you have, because you can have income that does not come from an employer (e.g. stock dividends).

[Nursie]

In the UK you get a code based on last year’s earnings, which the company uses to set a flat rate of withholding on each paycheck. If there’s any discrepancy that usually just feeds into next year’s code.

In Australia, you probably need to tell the companies about the other income sources, and they will attempt to withhold at the appropriate rate. Then at the end of financial year, you go to your pre-filled online tax return which has all the figures reported by each company you work for already present and sums up whether there’s a refund or payment due. This is also where you enter any deductions.