ATO Lodgement Deadlines & Penalties 2026: Your Complete Calendar

From tax returns to BAS and super payments, here's your complete ATO deadline calendar for 2025-26, with real penalty amounts.

By ECTD Editorial · Published 2026-08-10 · Updated 2026-08-10

Every year, thousands of Australians cop late lodgement penalties from the ATO – not because they're dodging tax, but because they simply forgot a deadline. In 2025-26, the penalties are steeper than ever, with the base penalty for a small business now $313 for each period a document is late (up from $222 in 2022-23). This guide walks through every key date you need to know, what happens if you miss one, and how to get out of a penalty if you've already slipped.

The 2025-26 financial year: key dates at a glance

The 2025-26 financial year runs from 1 July 2025 to 30 June 2026. Most individuals and small businesses need to lodge their tax return by 31 October 2026, but there are earlier deadlines for businesses with PAYG withholding, GST, and other obligations. Here's the full calendar:

28 July 2025 – Final day to lodge your 2024-25 tax return if you're using a tax agent and want it done early (agents have until 15 May 2026 for most clients).
28 July 2025 – Q4 2024-25 BAS and PAYG instalment due (for monthly lodgers, it's 21 July).
28 October 2025 – Q1 2025-26 BAS due (monthly: 21 October).
31 October 2025 – Deadline to lodge your 2024-25 tax return if you're doing it yourself (not via an agent).
28 February 2026 – Q2 2025-26 BAS due (monthly: 21 February).
28 April 2026 – Q3 2025-26 BAS due (monthly: 21 April).
15 May 2026 – Final deadline for tax agents to lodge 2024-25 returns for most individuals (but some agents have later dates).
28 July 2026 – Q4 2025-26 BAS due (monthly: 21 July 2026).

If you're a sole trader or small business with employees, you also need to pay super guarantee contributions by 28 July 2026 for the April-June quarter – and if you miss that, you face the super guarantee charge (SGC), which is a harsh 10% on top of the unpaid amount, plus interest and an administration fee.

What happens if you miss a deadline? The real penalties

The ATO's penalty system is not a slap on the wrist. For each document lodged late (like a tax return, BAS, or PAYG withholding report), you face a base penalty of $313 for small businesses (turnover under $10 million) and $626 for larger entities. But that's just the starting point – it can be multiplied based on how late you are:

Less than 28 days late: 1 penalty unit (0.5 for small businesses) – so $313 for a small business.
28 to 56 days late: 2 penalty units – $626.
57 to 84 days late: 4 penalty units – $1,252.
More than 84 days late: 8 penalty units – $2,504.

And if you have multiple documents late (e.g., your BAS for four quarters), those penalties stack. A small business that's 100 days late on four BAS documents could be looking at over $10,000 in penalties – before interest on any tax owed.

The 'failure to lodge' penalty is automatic: Unlike some other ATO penalties, the failure to lodge (FTL) penalty is applied automatically – the ATO doesn't need to prove you were negligent. It's only waived if you have a 'reasonable excuse' (like serious illness, natural disaster, or a death in the family) and you apply in writing. Forgetting is not a reasonable excuse.

What about interest on late payments?

If you owe tax and pay it late, the ATO charges the General Interest Charge (GIC) – currently 11.18% per annum for the March 2026 quarter (it's set quarterly). That's on top of any late lodgement penalty. For example, if you owe $10,000 in tax and pay three months late, that's roughly $280 in GIC alone. The ATO also charges a Shortfall Interest Charge (SIC) if you understate your income in a return – currently 7.18% per annum.

How to get a penalty remitted (and win)

The good news: the ATO remits (cancels) penalties more often than you'd think – if you ask properly. You need to write to the ATO, explain why you were late, and provide evidence. Common grounds that work: serious illness (with a doctor's certificate), a death in the immediate family, fire or flood, or if you relied on a tax agent who let you down (but you need proof they failed you, not just that they were busy).

If your excuse is 'I didn't have the money' – that doesn't work for late lodgement, but it can work for late payment penalties. The ATO is more lenient with GIC if you can show financial hardship and you've already lodged. Pro tip: always lodge on time, even if you can't pay. You can set up a payment plan after lodging – that avoids the FTL penalty, and the GIC is often reduced if you enter a plan early.

Lodge first, pay later: If you're struggling to pay your tax bill, lodge your return or BAS on time anyway. The ATO is very accommodating with payment plans (you can even apply online for automatic instalments if you owe under $100,000). Lodging late is the cardinal sin – it triggers the FTL penalty that's much harder to waive.

Using a tax agent? Your deadlines are different (and later)

If you use a registered tax agent, you get more time. Most agents have until 15 May 2026 to lodge your 2024-25 return, but they must have you 'on their books' – meaning you need to have engaged them before 31 October 2025. The same applies to BAS: if your agent lodges quarterly, they can often get an extra month. But here's the catch: you're still responsible for the deadline. If your agent misses it, the ATO can still penalise you – though you can argue 'reliance on agent' as a defence if you gave them all your info on time.

One more date to note: if you have a tax debt with the ATO, they can issue a 'notice of intent to disclose' to credit reporting agencies if you owe over $10,000 and haven't engaged with them. That can hurt your credit score for five years. So if you're in debt, contact the ATO before they contact you.

Your 2025-26 action plan: 5 steps to avoid penalties

Put every lodgement date in your calendar now – including BAS and super due dates, not just your tax return.
If you use a tax agent, confirm they have you on their books by 31 October 2025 – and give them everything by mid-April 2026.
Set up a separate bank account for tax (put aside 20-30% of every invoice) so you can pay on time.
Lodge even if you can't pay – then apply for a payment plan online via myGov or the ATO app.
If you miss a deadline, call the ATO immediately and ask for a remission – don't wait for the penalty notice.

What's new for 2025-26 that could trip you up

Two things to watch. First, the ATO's data-matching is getting sharper: they're now cross-referencing bank accounts, crypto exchanges, and even online selling platforms (like eBay and Etsy) in real time. If you have side income, it will show up. Second, the ATO has been cracking down on 'sham contracting' – if you're a sole trader but you work like an employee, the ATO can reclassify you and hit you with PAYG withholding penalties. That's a separate issue from lodgement, but it shows why staying on top of your obligations matters more than ever.

The bottom line: the ATO is not your enemy – but it is relentless. Miss a deadline and the penalties stack fast. But with a simple calendar, a tax savings account, and a habit of lodging even when you can't pay, you can sleep easy. And if you do slip, remember: a polite, well-evidenced remittance request works more often than not.

General information only — not personal financial, tax, legal or medical advice. Consider your own situation and consult a licensed professional before acting. Figures are current as at the date shown above.