The self-lodger deadline has now passed, and plenty of Australians who leave their return to a tax agent assume they have until May 2027. Many do. But the ATO's lodgment program for registered agents doesn't give every client the same date. If your most recent return came with a tax bill of $20,000 or more, your next deadline is likely to be 31 March 2027, about six weeks earlier.

The agent 'extension' is a program, not a single date

Registered tax agents lodge under a program the ATO sets each year. It spreads the workload across several months and sorts clients into tiers by risk and by how much they owe.

For the 2026–27 program, the ATO's published due dates for individuals and trusts set out three main lodgment points. Each tier is triggered by something different.

Commercial content published on 9 October made the same point from another angle. It said agent clients could have "potentially as late as May 17, 2027", but only subject to eligibility, and that extensions aren't automatic.

The first tier has already passed. Clients who had one or more prior-year returns still outstanding at 30 June 2026 had to lodge by 31 October 2026.

The second tier is the one that catches people out. Individuals and trusts whose latest return produced a tax Liability of $20,000 or more must lodge by 31 March 2027. The ATO excludes large and medium trusts from this tier, as they have their own program dates.

The third tier covers everyone else, including new registrations, with a due date of 15 May 2027. The ATO also lists 5 June as a concession date for 15 May returns. Those returns can be lodged by then "without penalty, provided that any payment required is also made by this date".

Two calendar quirks matter here. Both 15 May 2027 and 5 June 2027 fall on a Saturday, which explains why some commercial material refers to 17 May. The ATO's own table shows the unadjusted dates, so confirm the working date with your agent.

Why a $20,000 bill moves you up the queue

The ATO's table doesn't explain its reasoning. The practical effect, though, is plain: people who owed more last time are asked to lodge, and generally settle up, earlier.

Whatever the rationale, for the taxpayer it means the March date can arrive while they still think of tax time as a problem for winter.

The trigger is your latest return, not the coming one. Someone who had a one-off capital gain, a large Bonus or an Investment property sale last year could land in the March tier even if this year's income is ordinary.

The reverse is also true. A person who owed $20,000 or more last year but expects a refund this year still appears to fall in the March group under the published rules, because the test looks backwards.

When the bill is due depends on when you lodge

For clients in the 15 May tier, the ATO links the payment date to the date the return goes in. The earlier you lodge, the earlier you pay.

  • Lodge by 12 February 2027: pay by 21 March 2027.
  • Lodge between 13 February and 12 March 2027: pay by 21 April 2027.
  • Lodge from 13 March 2027: pay by 5 June 2027.

That structure means a 15 May client who expects a bill may have a reason not to rush. Lodging in late February rather than early February moves the payment date by a month.

There is a catch for anyone who misses their tier. The ATO says that for a late lodgment or a default assessment, payment is due 21 days after the lodgment due date. Lodging late does not buy extra time to pay.

Hypothetical example: two clients, one agent

Hypothetical example: Priya and Tom both use the same registered agent and were on the agent's books in time for the 2026–27 program. Neither had returns outstanding at 30 June 2026.

Priya sold shares last year and her 2025–26 assessment showed a tax liability of $24,500. Because that is $20,000 or more, she falls in the 31 March 2027 tier, despite her income returning to normal this year.

Tom's latest assessment showed a liability of $6,800, so he falls in the 15 May tier. If his agent lodges his return on 20 February 2027, the ATO's schedule makes any bill payable by 21 April 2027.

Priya's lodgment date is 45 days earlier than Tom's due date. Her liability last year was $17,700 larger than his, and that gap is what moved her into the earlier group.

The figures are illustrative only. Your own position depends on your assessment, your agent's records and the ATO's program rules.

Being on an agent's books matters

The later dates generally apply only to people who were already clients of a registered agent before the self-lodger deadline. Anyone who wasn't, and still hasn't lodged, shouldn't assume the program dates cover them.

The ATO's maximum failure-to-lodge penalty for individuals is $1,820, and it has stressed that late lodgment does not change when a bill falls due.

The rules described are the ATO's published program for registered agents, and individual circumstances vary.

Key dates to watch

  • 21 March 2027: payment due for 15 May clients who lodged by 12 February.
  • 31 March 2027: lodgment due for individuals and trusts whose latest return showed a liability of $20,000 or more.
  • 21 April 2027: payment due for 15 May clients who lodged between 13 February and 12 March.
  • 15 May 2027: lodgment due for remaining agent clients, including new registrations (a Saturday).
  • 5 June 2027: concession date for 15 May returns, provided any payment is made by then (also a Saturday).