This guide is for someone lodging their own 2025-26 income tax return, or thinking about handing it to a registered tax agent, with 31 October 2026 close or already gone. It rests on ATO pages and one Act, all read on 19 September 2026. InkCairn is an independent site, not the ATO and not a tax agent (see how guides are sourced), so where a step below is InkCairn’s reading rather than something the ATO states, the guide says so.
One detail is easy to miss: the date to lodge yourself and the date to sign up with an agent come from different ATO rules, and only the first may move when 31 October falls on a weekend.
The date to lodge by if you lodge yourself
The ATO says the due date to lodge your tax return is 31 October. That sentence names no year, but the same page is set up for the 2025-26 return, and the ATO’s 2026-27 agent program gives 31 October 2026 as the due date for a 2025-26 individual return where prior-year returns were still outstanding at 30 June 2026. InkCairn reads the two together as 31 October 2026. No ATO page for individuals read for this guide prints that full date.
31 October 2026 is a Saturday. The ATO has a general rule that when a due date to lodge or pay “falls on a day that is not a business day, you can lodge or pay on the next business day”. A business day excludes Saturday, Sunday and a public holiday for a whole state or territory. That rule sits on a page for tax professionals, and no ATO page read for this guide applies it to a self-lodger’s 2025-26 return in so many words.
The ATO rule: a lodgment date that is not a business day can be met on the next business day. InkCairn’s suggestion: work to 31 October 2026 and treat the weekend rule as a fallback, not a plan.
If you use a registered tax agent
Most registered tax agents have a lodgment program and can lodge returns for their clients after the usual 31 October deadline. The ATO tells individuals that the due date for your return “will depend on your personal situation as well as when you engage your tax agent”. If you are new to an agent or changing agent, “you should contact them before 31 October to be part of their lodgment program.” The ATO also says tax agents must be registered with the Tax Practitioners Board.
The condition that decides this is on the ATO’s page for agents. To cover a client with its lodgment program, an agent must notify the ATO of its authority to act by 31 October 2026 for income tax, and the ATO adds: “You can’t notify us on the next business day.” The weekend rule above does not stretch that cut-off. If you were previously a self-preparer and an agent takes you on after 31 October 2026, the ATO says you “will not be covered by your lodgment program and may need to lodge by an earlier due date”.
InkCairn’s suggestion: if you want an agent’s later date, contact one well before 31 October 2026 and do not leave it to the next business day, because the agent has to make the notification by that date.
These are the ATO’s 2026-27 program dates for individuals. The ATO calls the list “a guide only” and says the date an agent gets for a client depends on factors including when the client was added to the agent’s list, so ask your agent to confirm yours.
| Your situation | Date in the ATO’s 2026-27 agent program |
|---|---|
| One or more prior-year returns were outstanding at 30 June 2026 | 31 October 2026, unless all overdue returns are lodged by 31 October 2026, in which case your normal program date applies |
| Your latest return had a tax liability of $20,000 or more | 31 March 2027 |
| Individuals not required earlier | 15 May 2027. The ATO also lists a separate 5 June concession, so ask your agent whether it applies to you |
Can you still lodge after the due date?
Yes. A late return can still be lodged, and the ATO says “it’s important to get up to date as soon as possible to reduce the risk of penalties and interest.” The sections below cover what the ATO says may follow, and how to ask for less of it.
Will there be a penalty, and how much?
It depends. The ATO says that “Generally, we don’t apply penalties in isolated cases of late lodgment”, and that it warns by phone or in writing before applying one. For a late tax return that results in a refund or a nil result, the ATO says it generally will not issue a failure-to-lodge (FTL) penalty notice, unless a penalty was applied before the return was lodged, the document is a third-party data report, or you are classified as a large withholder.
When a penalty does apply, the ATO works out the base FTL penalty as one penalty unit for every 28 days (or part of a 28-day period) that the document is overdue, up to a maximum of 5 penalty units. The base amount applies to individuals.
The ATO’s penalty units table gives $364 for an infringement on or after 1 July 2026, and $330 for 7 November 2024 to 30 June 2026. The Crimes Act 1914 (section 4AA) sets the penalty unit at $330 subject to indexation, and indexes it on 1 July 2026 and every third 1 July after that. InkCairn took $364 from the ATO’s table, because the Act’s text does not carry the indexed figure.
InkCairn is not printing a dollar total for a late return. The ATO’s table is keyed to when an infringement occurred, and its penalty page does not say when that is for a return due on 31 October 2026, so any total would rest on a guess about which row applies. The 28-day steps and the cap are the ATO’s; the total is left to the ATO.
A penalty notice gives a payment date at least 14 days after the notice. You can’t claim a deduction for penalties the ATO imposes.
Interest on unpaid tax
General interest charge (GIC) is separate from the penalty. The ATO says GIC may apply to unpaid tax, including where a return is lodged late, and that it is calculated daily on a compounding basis on the amount overdue. The ATO’s page for agents says that if a return is lodged late, any tax is payable 21 days after the due date for lodgment.
The ATO reviews the GIC rate quarterly, so InkCairn does not print one. The ATO’s general interest charge page is the place to start. GIC incurred on or after 1 July 2025 can’t be claimed as a deduction.
InkCairn’s reading, not an ATO statement: GIC is charged on an amount that is unpaid, so a return that ends in a refund carries no GIC from being lodged late. The ATO’s page does not put it in those words.
If a return is left unlodged
The ATO says that after the due date it contacts people by SMS, myGov messages, letter or phone, and that a penalty may be applied. For people who do not engage with it, the ATO’s page lists firmer steps: a final notice, a default assessment, an audit, keeping a refund until lodgment is made, and prosecution. It says a default assessment attracts a 75% penalty of the tax-related liability, and that failing to lodge is a criminal offence which, on conviction, can bring fines and/or up to 12 months’ imprisonment.
The ATO writes these steps for people unwilling to work with it, and it does not describe them as the outcome of a single late return. That page was last updated on 25 January 2024, older than the other ATO pages used here, and InkCairn cites the figures as the ATO’s statement without having checked them against the Act.
Asking for more time, or for a penalty to be removed
Before the due date. The ATO says: “If you can’t lodge on time, phone us before the due date so we can work together to reduce the risk of a penalty.” The number for individuals is 13 11 42. The ATO also names a registered agent (who may mean a later due date), Tax Help and the National Tax Clinic program as lodgment support for individuals.
After a penalty. Lodge the outstanding return first: the ATO says you will be expected to lodge outstanding documents before you request remission. Individuals can request remission of interest charges or an FTL penalty by phone, or by mail or online services using the ATO’s form for each type. The ATO says it may remit GIC if there are extenuating circumstances.
For FTL penalties, the ATO lists reasons it is likely to accept, such as severe illness, a missing income statement, a disaster or family violence, and reasons it is likely to decline, such as a holiday, work, a cold, not receiving a reminder, or not having lodged yet. The ATO’s page on how to request a remission carries a notice about changes to its remission request processes while it awaits the outcome of a broader review of taxpayer relief provisions, so check that page for the current steps.
If you used a registered agent. The ATO describes a safe harbour if you engaged a registered agent: you won’t be liable for an FTL penalty if you can show you gave the agent all relevant tax information to enable them to lodge the return or statement by the due date, and the agent’s failure to lodge was not because they were reckless or intentionally disregarded the tax law. You need evidence that you supplied the information.
If you can’t pay
InkCairn’s suggestion: do not hold the return back because you can’t pay. The ATO’s tax support page says that before it can consider an individual’s application for release from certain tax debts on financial hardship grounds, you must lodge all your outstanding tax returns and activity statements so it knows the total amount you owe.
If you are in financial difficulty you may be eligible for a payment plan. The ATO says tax debts on a payment plan continue to accrue GIC, which compounds daily, and that any refunds or credits you are entitled to will be used to reduce the debt. The ATO’s number for people who can’t lodge or pay on time is 13 11 42.
If you don’t need to lodge
If you work out that you don’t need to lodge a return, the ATO says to tell it by lodging a non-lodgment advice (also called a return not necessary), online through myGov or on a paper form. That stops the ATO sending reminders. The ATO says you usually don’t need to lodge if your income is under the tax-free threshold and no tax was withheld from it, with exceptions listed on its page. InkCairn does not print the threshold here, because that page gives it with no income year. Check it against the 2025-26 income year before you rely on it.