If I do not have ITR documents, what can I show as proof of source of funding for the Australian visa?

If you don't have ITR documents, you can use recent bank statements showing a stable balance, an educational loan approval letter, scholarship or sponsorship letters, or financial documents from a parent or sponsor such as their bank statements and income proof. Make sure all documents are clear, in English, and can show genuine access to funds. Avoid sudden large deposits without explanation.