What Happens If You Miss a Tax Return Lodgement Deadline?

Most Australian taxpayers know they must lodge a tax return each year. However, many underestimate what happens if they miss the deadline. The ATO takes a missed tax return deadline seriously. Not only does it affect revenue, but failure to lodge is also one of the key risk flags the ATO uses to select taxpayers for closer scrutiny.

This article explains the consequences of a missed tax return deadline, the penalties that may apply, and what to do if you have returns outstanding.

What Are the Tax Return Lodgement Deadlines?

If you lodge your own return, the standard due date is 31 October after the income year ends on 30 June. If you lodge through a registered tax agent, a later date generally applies, often 15 May of the following year.

Note that the later agent date can be lost. If prior-year returns are still overdue at 30 June, your current-year return is generally due by 31 October instead (ATO: taxpayers with overdue tax returns).

Companies, trusts and partnerships have their own deadlines, which depend on the entity type and whether a tax agent is engaged. In addition, employers and businesses have separate obligations for BAS, PAYG reporting and other ATO reports.

If you miss any of these deadlines without a valid reason or an ATO extension, penalties and other consequences can follow.

The Failure to Lodge Penalty for a Missed Deadline

The ATO can impose a failure to lodge (FTL) penalty when you do not lodge a required document on time. The penalty is based on penalty units. From 1 July 2026, one penalty unit is $364, up from $330 (ATO: penalty units).

For individuals and small entities, the FTL penalty is one penalty unit for each 28 days (or part of 28 days) that the return is late, up to a maximum of five units ($1,820). The amount is doubled for medium entities and multiplied by five for large entities. For significant global entities, it is 500 times the base amount, a maximum of $910,000 (ATO: failure to lodge on time penalty).

The ATO can remit the FTL penalty in part or in full where there are acceptable reasons for the delay. In our experience, a one-off late lodgement with a good history and a prompt catch-up often results in remission.

Multiple Years of Overdue Tax Returns

One missed year can easily become several. Many people who fall behind find the task more daunting each year. As a result, a cycle of avoidance sets in and several years of returns end up outstanding at once.

Where returns are not lodged, the ATO can issue default assessments, which are its own estimate of your liability. These estimates are often unfavourable and may overstate the tax you actually owe. What’s more, a default assessment can attract an administrative penalty of 75% of the resulting tax-related liability, on top of the tax itself. See our guide to ATO penalties for more on how these penalties work.

In one matter, a client with a long-term medical condition had not lodged returns for several years. We obtained remission of all penalties and general interest charges because the client’s circumstances had prevented timely lodgement. This saved the client a substantial amount.

What to Do If You Have Missed a Tax Return Deadline

If you have one or more years of returns outstanding, deal with them before the ATO acts. Lodging voluntarily, even late, is always better than waiting for a default assessment or enforcement action.

Also remember that unpaid tax attracts general interest charge, which compounds daily. The GIC rate is 11.51% a year for October to December 2026 (ATO: GIC rates). In addition, GIC incurred on or after 1 July 2025 is no longer tax deductible.

At Australian Tax Experts, we regularly help clients with several years of overdue tax returns, often in difficult circumstances. We prepare and lodge the outstanding returns, negotiate with the ATO on penalties and interest, and bring your affairs back into order as efficiently as possible.