The ATO advises that the Tax Agent Portal allows agents to view the lodgment status of the current year and last three years' income tax returns for a client. From the same screen agents can advise that a return is not necessary (RNN), or that further returns are not necessary (FRNN). Previously, the portal displayed up to 19 years of outstanding income tax returns. Due to some recent system changes, it will now only display outstanding years from 2001 onwards.
For a copy of the ATO advice and more information about obtaining a client’s outstanding lodgments prior to 2001, go here