Income tax is levied on taxable income. Taxable income is calculated as [assessable income] less [any allowable deductions]. Deductions include wages, cost of stock, rent, bad debts, and previous year losses.
Sole traders are not required to complete a separate return for their business. They use their personal income tax return to report their business income and deductions.
Partnerships complete a partnership tax return to show the partnerships income and deductions and how the profit or loss was shared among partners.
Companies complete a company tax return to calculate the income tax the company should pay. Income tax is calculated according to taxable income for sole traders. Trusts complete a tax return and distribute income to beneficiaries or unit holders.
NOTE: Resident tax rates do not include the Medicare levy
Click here to access the ATO's tax withheld calculator for individuals