We have a Medicare levy of 2%. This is a tax. Our Medicare scheme is broader than yours. We have a superannuation contribution of 12%. This is not a tax, it is 12% of your gross income compulsorily paid by your employer into a superannuation fund of your choice. You can't withdraw from it until you retire. You can optionally pay more in at any time. The account itself is in your name and under your control.

If you are self-employed, you have to pay both the employer and employee portion.

For example, Social Security and Medicare taxes are 7.5% paid by the employee and 7.5% paid by the employer. (That isn't the exact value. I'm using round numbers.) If you work as an employee, you only see 7.5% deducted from your paycheck. If you are self-employed, you have to pay the full 15% = 7.5% + 7.5%.

There are other taxes, like unemployment insurance, that you have to pay if self-employed.

In the US, a portion of payroll taxes is called "FICA" taxes - essentially your share of social security payments (essentially a federalized retirement pension) plus Medicare contribution (toward the Medicare program, which is a default health insurance available to those 65 and older.)

The taxes on each wage earner are divided into an employer paid part and the earner's portion, both equal, which is 7.65%. So the total FICA burden on the wagie is 15.3%. But the wagie only sees the wage earner side of 7.65% deducted on their paycheck.

A self employed person must pay both sides of this FICA burden. Therefore as a self employed you pay the entire 15.3%.

Even though it seems simple it's just complex enough to trip up many unprepared normies who believe that they get to "keep everything" as a contractor.