It is 1 September. There are 60 days until 31 October, and for anyone carrying an unlodged tax return from a previous year, that date does more work than any other in the calendar.
The usual understanding is that using a tax agent buys you until May. It does, but only if your record is clean. If even one prior year return was outstanding on 30 June 2026, the Australian Taxation Office has already moved your 2026 return to 31 October 2026, and no agent can move it back by asking.
Three separate things happen on 31 October 2026
People treat it as one deadline. It is three, and they apply to different people.
| Who you are | What 31 October 2026 is |
|---|---|
| You lodge your own return and your past years are up to date | Your normal deadline for the 2026 return. |
| You want an agent’s later due date but are not on an agent’s client list yet | The final date a registered agent can add you to their client list for your 2026 return to be covered by the lodgment program. |
| You had one or more prior year returns outstanding at 30 June 2026 | Your 2026 return is due on this date regardless of who lodges it. The extension is restored only if every overdue prior year return is also lodged by 31 October. |
Source: ATO, Registered agent lodgment program, October 2026 due dates, and Check your clients’ lodgment due dates. Retrieved 1 September 2026.
31 October 2026 is a Saturday, and it does not move
The ATO’s general rule is that when a due date falls on a weekend or public holiday, you can lodge or pay on the next business day. Overdue returns are carved out of that rule. The ATO states it plainly:
“If all overdue prior year returns are lodged by 31 October, the current year tax return will be due as per your lodgment program. You can’t lodge overdue prior year returns on the next business day.“
Source: ATO, Check your clients’ lodgment due dates. Retrieved 1 September 2026.
Monday 2 November is not a grace period for this. Neither is Sunday 1 November. If you are working backwards from a date, work backwards from Saturday 31 October.
The order most people get backwards
The instinct is to deal with the current year first, since that is the one with a deadline attached, and get to the old ones later when there is time.
That sequence produces the worst outcome available. Lodging the 2026 return does nothing to your due date, because the due date was set by what was outstanding on 30 June. Lodging the overdue years is what restores the extension, and it restores it for the current year as well.
So the sequence is: oldest outstanding year first, forward to 2025, then 2026 last with the time that gets handed back to you. The ATO notes the updated due dates can take up to three weeks after 31 October to appear in its systems, which is a display lag rather than a problem.
What the penalties actually are
The failure to lodge on time penalty is one penalty unit for every 28 days, or part of 28 days, that a document is late, capped at five penalty units. The cap matters: the meter stops at 140 days. A return three years late attracts the same maximum as one 141 days late.
The penalty unit amount changed on 1 July 2026. A lot of published guidance still quotes the old figure.
| When the infringement occurred | Penalty unit | Maximum FTL penalty per document |
|---|---|---|
| On or after 1 July 2026 | $364 | $1,820 |
| 7 November 2024 to 30 June 2026 | $330 | $1,650 |
| 1 July 2023 to 6 November 2024 | $313 | $1,565 |
Source: ATO, Penalty units and Failure to lodge on time penalty. Retrieved 1 September 2026. Figures above are for individuals and small withholders; medium and large withholders have the base penalty multiplied by 2 and 5 respectively.
Now the part that is missing from most of what gets written about this. The ATO’s own published position is that it generally will not issue an FTL penalty notice for a late-lodged tax return where the lodgment results in a refund or a nil result, unless the penalty had already been applied before you lodged. For a large share of people sitting on old returns, particularly employees with tax withheld from wages, those years produce refunds. The penalty they have spent years avoiding was never going to be charged.
The ATO also says it will generally warn you by phone or in writing, and issue a notice to lodge, before applying an FTL penalty. Penalties are not the ambush most people picture.
The cost that is real: interest on what you owe
Where an old year produces tax payable rather than a refund, the general interest charge applies from the date the tax should have been paid. GIC is calculated daily and compounds. The rate for the July to September 2026 quarter is 11.43% a year. The ATO reviews it quarterly and publishes each rate roughly two weeks before the quarter starts, so the October to December figure is not out yet.
Two things make this heavier than a bank interest rate at the same number. It compounds daily on the running balance, and since 1 July 2025 GIC can no longer be claimed as a deduction. A pre-2025 GIC bill was partly offset at your marginal rate. A current one is not offset at all.
This is the reason the arithmetic favours lodging even when you expect to owe. The debt is already accruing. Lodging does not start the interest, it stops the balance it runs on from growing further, and it opens the door to a payment plan.
Some of those years may not need a return at all
Not every gap in your lodgment history is an unlodged return. Where you genuinely had no obligation to lodge for a year, what the ATO wants is a non-lodgment advice, sometimes called a return not necessary. It is a short declaration, not a return.
The practical shapes of this: a year spent overseas with no Australian income, a year on a student visa under the tax-free threshold with no tax withheld, a year out of the workforce. Note the “no tax withheld” part. If any tax was withheld, a return is usually worth lodging because that is how the money comes back.
The lodgment windows are different for the two, and the difference is large:
- Tax returns online through myTax: back to 2016. The 2014 and 2015 years are possible if you meet the eligibility conditions. For 2013 and earlier, it is a paper return or a registered agent.
- Non-lodgment advice online: back to 2000.
Someone with six blank years often turns out to need two returns and four non-lodgment advices. That is a very different afternoon from the one they were dreading.
What happens if you keep waiting
The ATO’s stated preference is to work with you. Where that does not happen, it can issue a default assessment: its own estimate of your taxable income, built from what employers, banks and government bodies have already reported about you, plus asset and lifestyle data.
A default assessment carries an administrative penalty of 75% of the tax-related liability, and that can rise to 90% where there is a pattern of non-compliance. FTL penalties can apply on top. To challenge the figure you have to lodge a formal objection and prove your actual position, which means producing the records you did not have when you were avoiding the return in the first place.
The ATO sends a warning letter with a lodgment date before issuing one, except in narrow circumstances such as a risk of the taxpayer leaving the country or assets being moved offshore.
💡 The expensive outcomes here are the ones that come from waiting, not from lodging. Penalties are capped, often not charged at all on refund years, and can be remitted. Interest compounds daily and is no longer deductible. A default assessment starts at 75%.
How to work through it in the next 60 days
- Find out what is actually outstanding. Sign in to myGov, go to ATO, then Tax, then Lodgments. Do not work from memory. People are routinely wrong in both directions about which years are missing.
- Split the list into two piles. Years with income or withheld tax need a return. Years with neither need a non-lodgment advice.
- Pull income statements and pre-fill for each year. Most of the data you need is already held by the ATO. Older years are thinner, which is where bank statements and old payslips do the work.
- Lodge oldest first. Every year you clear moves you closer to having the 2026 extension restored.
- If you are engaging an agent, do it now rather than in late October. Adding a client to an agent’s list and getting several years of records together are not same-week activities.
- Ask about a deferral if the volume is genuinely large. Where an agent takes on a new or re-engaged client with overdue returns, the ATO has a specific deferral for that situation, which can provide a deferred due date for the current year return and suspension of compliance action on the prior year returns while the catch-up happens. It is requested by the agent, not by you.
- Lodge first, then ask about penalties. Remission can be requested where circumstances warrant it, but the ATO expects the outstanding documents to be lodged before it considers the request.
If your affairs are current and this is only about the 2026 return, the timing question is a different one, and we covered when to lodge and why early July is usually the wrong answer separately. If a return is already in and the money has not arrived, the reasons refunds get held or reduced covers that ground.
Frequently asked questions
How many years back can the ATO make me lodge?
There is no cut-off after which an unlodged return stops being required. An obligation to lodge does not expire with time. Practically, online lodgment through myTax reaches back to 2016, with 2014 and 2015 available if you meet the eligibility conditions, and 2013 and earlier handled on paper or through a registered tax agent. Non-lodgment advice can be lodged online for income years back to 2000.
Will I be penalised for lodging late?
Possibly not. The failure to lodge penalty is one penalty unit per 28 days or part thereof, capped at five units, which is $1,820 per document for infringements on or after 1 July 2026 at the current $364 penalty unit. The ATO’s published position is that it generally will not issue an FTL penalty notice for a late-lodged return where the lodgment results in a refund or a nil result, unless the penalty was applied before lodgment. It also generally warns you before applying one.
I have prior year returns outstanding. Can a tax agent still get me until May?
Not directly for 2026. If one or more prior year returns were outstanding at 30 June 2026, the 2026 return is due 31 October 2026. If every overdue prior year return is lodged by 31 October 2026, the 2026 return reverts to the lodgment program due date. Where the catch-up is large, an agent can request a new or re-engaged client deferral, which can provide a deferred due date for the current year and suspension of compliance action on the prior years.
31 October 2026 is a Saturday. Do I get until Monday?
Not for this. The ATO’s weekend and public holiday rule allows lodging or paying on the next business day for standard due dates, but it states specifically that overdue prior year returns cannot be lodged on the next business day. Treat Saturday 31 October 2026 as the date.
What if I owe money and cannot pay it?
Lodging and paying are separate obligations, and the penalties attach to lodging. Lodging tells the ATO the real figure, which is what a payment plan is built on, and it stops the failure to lodge exposure growing. General interest charge continues to apply to the unpaid amount, currently 11.43% a year for the July to September 2026 quarter, calculated daily and compounding, and since 1 July 2025 it is not deductible.
What if the ATO has already issued a default assessment?
A default assessment is the ATO’s own estimate of your taxable income and carries an administrative penalty of 75% of the tax-related liability, rising to 90% where there is a pattern of non-compliance. It is not corrected by lodging the return afterwards. You have to lodge a formal objection setting out why you are dissatisfied, supported by evidence, and you can object to the penalty assessment separately. This is worth getting help with.
Talk it through
Send us what you actually know: which years you think are missing, whether you had tax withheld in those years, whether you were overseas for any of them, and whether the ATO has written to you. We will work out which years need a return, which need a non-lodgment advice, and what 31 October means for your particular position.
👉 Book a 20 minute call, or phone us: Melbourne 03 9600 0803 | Brisbane 07 3188 8081.
Multi-year catch-up work sits across bookkeeping, reconstruction of old records and lodgment, and at Wiselink all three happen in the same practice, split by function with senior review on the work that carries risk. That matters here more than usual, because the years being reconstructed have to hang together as a set. If the wider question is whether your accountant is handling the year ahead rather than only reporting the one behind, the planning versus compliance check sets out what to look for.
Credentials: CPA, Registered Tax Agent, ASIC Registered Agent, NTAA member, Xero, MYOB and QuickBooks partner, in practice since 2013. Our registration can be checked on the TPB public register. We work in English and Mandarin.
📍 Melbourne Camberwell (1381 Toorak Rd, Camberwell VIC 3124) · Brisbane Eight Mile Plains (3 Clunies Ross Court, Eight Mile Plains QLD 4113)
Sources
- ATO, Penalty units (penalty unit amount table), last updated 26 June 2026. Retrieved 1 September 2026.
- ATO, Failure to lodge on time penalty, last updated 22 June 2026. Retrieved 1 September 2026.
- ATO, Check your clients’ lodgment due dates, last updated 1 July 2026. Retrieved 1 September 2026.
- ATO, Taxpayers with overdue tax returns, last updated 1 July 2026. Retrieved 1 September 2026.
- ATO, Registered agent lodgment program, due dates by month, October 2026. Retrieved 1 September 2026.
- ATO, General interest charge and General interest charge (GIC) rates. Retrieved 1 September 2026.
- ATO, Default assessments for overdue lodgments, last updated 1 July 2026. Retrieved 1 September 2026.
- ATO, Lodge a prior year tax return and Lodge a non-lodgment advice. Retrieved 1 September 2026.
- ATO, Clients and your client list (new or re-engaged client lodgment deferral). Retrieved 1 September 2026.
Written by Lily Zhang, CPA and Registered Tax Agent, founder of Wiselink Accountants. Last reviewed: 1 September 2026.
This article is general information, not advice for your circumstances. All dates, rates and penalty amounts are taken from ATO published guidance as retrieved on 1 September 2026 and can change; the general interest charge rate is reset quarterly and the October to December 2026 rate had not been published at that date. Penalty remission is at the ATO’s discretion and is not guaranteed in any particular case. Whether a year requires a tax return or a non-lodgment advice depends on your own circumstances and should be confirmed with a registered tax agent. Liability limited by a scheme approved under Professional Standards Legislation.
