My IELTS result was over 3 years old (Result should not be older than 12 months at the time you applied for the visa), it is now a requirement for primary applicant to provide evidence of functional English.
There are other ways to prove it depending on your situation.
Provide a letter (Certificate) from University or School to confirm Medium of Instruction is English. It will be accepted if
1. You completed 2 year full-time study for a degree, a higher degree, a diploma or a trade certificate in an institution in or outside Australia .
2. All years of primary and at least 3 years of secondary study at primary school and secondary school where all instruction was in English in or outside Australia
3. At least 5 years of study at a secondary school in or outside Australia where all instruction was in English
Hope this helps