Picture a Clayton electrician in the last week of October, completely relaxed. He has an accountant, so he assumes the 31 October tax return deadline is not his problem. What he actually has is someone who did two of his returns years ago. He is not on anyone’s client list now, and his return is due within days.
The gap between having an accountant and being on a registered agent’s client list is where that date does its quiet damage. This year there is an extra wrinkle worth knowing about now, not on the last Friday of the month.
The 31 October tax return deadline moves in 2026, but only for some people
31 October 2026 falls on a Saturday. The ATO’s general rule is that when a lodgement or payment date lands on a weekend or public holiday, you can lodge or pay on the next business day. So if you lodge your own 2025-26 return, you have until Monday 2 November 2026.
Two agent cut-offs do not move with it. The ATO confirmed on 3 September 2026 that overdue prior year returns must be lodged, and new clients added to an agent’s client list, by that Saturday rather than the Monday. That rule is specific to the lodgement program.
One date shifts. The other does not.
Being with an accountant is not the same as being on their client list
Eligible clients of a registered tax agent can get a later due date under the ATO’s lodgement program. For many individuals and trusts not required to lodge earlier, that date is 15 May 2027, and some qualify for a further concession to 5 June 2027, provided any tax owing is paid by then. Due dates vary by taxpayer though, and the later date is not automatic.
You also have to be on the client list before 31 October. If you run a company, trust, partnership or SMSF, part of that sits with you. Entities with an ABN, other than sole traders, must nominate their agent through client-to-agent linking in ATO online services before the agent can add them. Individuals and sole traders are exempt for now.
If you have never used it, allow time rather than leaving it until late October.
One unlodged return from an earlier year drags you back
Here is the part that catches people who have used an agent for years. If one or more prior year returns were outstanding as at 30 June 2026, your current return is due 31 October and the May concession does not apply.
To get the ordinary program date back, those overdue returns must be lodged by 31 October, not after. The ATO says the new date can take up to three weeks to show on its systems.
What missing it actually costs
How badly missing the 31 October tax return deadline hurts depends on your circumstances. The ATO generally does not penalise isolated late lodgements, and it warns you first. But the numbers moved this year. The failure to lodge penalty is one penalty unit for every 28 days, or part of a period, that a document is late, capped at five units. At $364 per unit from 1 July 2026, up from $330, the base maximum is $1,820 per document. That base rate covers individuals and small withholders, with higher multipliers for larger entities.
Interest is separate, and attaches to unpaid tax rather than late paperwork. Where an assessed amount stays unpaid after its payment due date, the general interest charge (GIC) applies. For the October to December 2026 quarter it is 11.51 per cent, compounding daily, and GIC incurred from 1 July 2025 is generally not deductible. That lifts the real after-tax cost of carrying an ATO balance.
Two things take the edge off. The ATO generally does not issue a failure to lodge penalty where the return produces a refund or a nil result, though exceptions apply. And if you engaged a registered agent, gave them everything in time to meet the due date, and the agent was not reckless or deliberately ignoring the law, safe harbour can protect you from the penalty. You have to request it and back it with evidence.
The BAS can land in the same week
If you report quarterly, the standard due date for your September quarter BAS is 28 October 2026. Lodge online and you may get an extra two weeks, and an agent’s concession can move it further again. A quarter one PAYG instalment notice may fall due too. The date on your activity statement is the one that counts.
What to do before the 31 October tax return deadline
Check whether you are actually listed with your agent. Ask them directly and get a yes or no. “I have used them for years” is not the same answer.
Self-lodging? Start pulling your paperwork together. Employer income statements and bank interest usually pre-fill. Other income, rental figures and deductions may be missing or incomplete, so check them against your records.
And remember that lodging and paying are separate. Lodge your own return on time and payment is generally due 21 November, or 21 days after your assessment if it issues after 31 October. Lodge late and the payment date does not move. Go by the date on your notice of assessment.
Not sure where you stand?
If you would rather not spend the last week of October working out whether you are on someone’s client list, have a chat with us first. It is usually a quick conversation. You can see how we work with business owners on our business services page, or get in touch on 1300 888 168. And if the real worry behind the deadline is cash, our note on resetting cash flow after EOFY covers the practical side.
This article is general information only, is current at 5 October 2026 and does not take your circumstances into account. ATO due dates vary by taxpayer and can change. Check your own due dates in ATO online services, with your registered tax agent, and on any notice of assessment before acting.