Too many questions! You need a LOT of help with this. You have no choice but to consult with a tax accountant to have all your questions aswered in accordance with your individual circumstances. You might also need an experienced bookkeeper to put all your figures correctly into MYOB or Quickbooks.Your net income from business (that you are assessed to pay income tax on) will just be calculated as per your accounting records of business income received less business expenses paid during the tax year (if using the cash basis tax accounting method - which is usually done by small business and is a good idea if you can claim the Entrepeneur's Tax Offset).Note - a sole trader cannot be an employee of themselves. So you do not do PAYG withholding on your personal drawings from your bank account. What you withdraw from the bank is never wages, just drawings of your own money. Ask your tax accountant about PAYG instalment obligations which will arise after you lodge your first tax return with a business profit. In the meantime, set aside at least 25% of your income for Notice of Assessment tax payable after you lodge the tax return.Good luck