There are various methods ATO have approved. You can choose one method which is easy or beneficial to you. However, for every method, you need to keep the supporting calculation and/or documents. We can have with ready-made templates if you are not ...
1 You have incurred the cost to earn the income directly 2 You have documentary proof 3 You have not claimed it from anyone else (e.g. reimbursement or cost-sharing)