Sorry, perhaps I wasn't clear enough.
In relation to paying tax only on your profits, I You asked:
"How can I open a business bank account and avoid paying tax on all of my revenue and only pay tax on profit."
"What you have to do is keep records of both your revenue and expenses so you can declare both in your tax returns and activity statements and you should then normally only be taxed on the difference."
The difference between revenue, less your expenses is your profit, and that is what you will pay tax on if you maintain records of of both your revenue and expenses and report these figures in your tax returns.
If your request for a further answer is directed at how you open an an account, the answer is that you will generally need to involve your legal gaurdian, and open the account directly with your guardian's signed approval or have an adult appointed to run the account in your stead as a trustee. This is because when you open a bank account you are essentially entering into a contract with the bank, and as a minor you generally are not considered to have the legal capacity to contract unless a legal guardian has approved the contract.
I trust that answers your question.
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