The ATO advises that from 1 July 2013, agents will be required to lodge 85% or more of their clients' current year returns by the lodgment program due date, or by the deferred due date if a deferral is granted.
Additionally, concessional lodgment dates available under the lodgment program will only apply to returns lodged electronically. If a paper return is lodged after the statutory due date, late lodgment penalties may be applied.
For more information, go here
For a copy of the ATO document "Lodgment program framework - frequently asked questions", go here