The deadline for lodging your own individual tax return is the 31st of October, lodging any later than this can incur penalties.
if you are unable to lodge by 31st October, you will need to contact the ATO as soon as possible.
Most registered agents are able to lodge returns for clients later than the 31st of October due to having special lodgement schedules. If you are using a registered agent, ensure you contact them before 31st October. Should you be needing a registered agent, please contact DD's Taxation and Accounting Centre.