You Haven't Lodged BAS in Months. Here's What Actually Happens Next.

Most people who are badly behind on their Business Activity Statements didn’t decide to be. It usually goes: one quarter got away in a busy month, the next one felt too big to face without fixing the first, and after that the whole thing became something to not think about. By the time there’s a letter sitting unopened, the problem has stopped being administrative and started being emotional.

So let’s take the emotion out of it and look at the mechanics, because the mechanics are more manageable than the dread, and one part of them is genuinely more urgent than most people realise.

What the ATO actually does, in what order

The Australian Taxation Office is a long way from the debt collector of popular imagination, particularly for a small business that hasn’t been contacted before. The sequence is broadly predictable.

First come reminders, through myGov, your online services account, and by letter or SMS. These are automated and they are not a threat, though they don’t feel that way when there are five of them. Then, if nothing happens, contact becomes more direct: phone calls, and firmer letters that name specific outstanding periods and give a date.

If there’s still no response, two things become available to the ATO that you’d rather avoid. They can issue a default assessment, estimating what you owe from whatever information they hold: your reported turnover, industry benchmarks, previous statements. And they can begin recovery action on the resulting debt.

Prosecution exists, but it is rare and it sits at the end of a long road of ignored contact. Almost nobody reading this is on that road. The realistic risk isn’t prosecution; it’s a default assessment plus compounding interest, which is a slower and quieter kind of expensive.

How much is the penalty for lodging BAS late?

The failure to lodge penalty is mechanical, which makes it easy to work out in advance.

For a small entity, it’s one penalty unit for each 28-day period, or part of a period, that the document is overdue, capped at five periods. The Commonwealth penalty unit is $364 for lateness from 1 July 2026, having been indexed up from $330.

Two things to notice. The penalty stops growing after five periods, so a statement two years overdue attracts the same failure to lodge penalty as one four months overdue. That’s the good news, and it’s the reason panic isn’t useful here.

The bad news is the phrase per document. Each outstanding activity statement carries its own penalty. Eight overdue quarterly statements at the maximum is eight lots of $1,820, and none of that touches the tax itself.

A small entity here means turnover under $1 million. Between $1 million and $20 million the penalty doubles; above that it’s multiplied by five.

The part that’s actually urgent: interest

The penalty is capped. Interest isn’t, and this is where the real cost sits, particularly since a change that took effect on 1 July 2025 and that a lot of business owners still haven’t been told about.

General interest charge applies to any tax liability you haven’t paid by its due date, including overdue activity statements. It’s calculated daily on a compounding basis and reviewed each quarter. For the July to September 2026 quarter it’s 11.43% per annum.

Here’s the part that changed. General interest charge and shortfall interest charge used to be tax deductible, which meant a business in a moderate tax bracket effectively carried an ATO debt at a discount. From 1 July 2025, that deduction is gone, and it’s gone regardless of how old the underlying debt is. Interest accruing today on a 2022 activity statement is not deductible.

The practical consequence is worth stating plainly, because it reverses advice that was sound for years: for many small businesses, an ATO debt is now more expensive than commercial finance. An 11.43% daily-compounding charge with no deduction against it is not a cheap line of credit, and it used to be treated as one.

What changes the moment you engage

Almost every mechanism that reduces what you owe is triggered by you making contact first. That’s not a moral position on the ATO’s part, it’s just how the provisions are written.

Voluntary disclosure

If there’s a shortfall (you under-reported, or claimed something you shouldn’t have), telling the ATO before they notify you of an examination reduces the base shortfall penalty by 80%. If the shortfall is under $1,000, it’s reduced to nil. Make the same disclosure after they’ve contacted you and the reduction typically drops to around 20%. Same facts, same disclosure, materially different bill, decided entirely by sequence.

Safe harbour when it was your agent’s failure

If you gave your registered agent everything they needed in time and they didn’t lodge, you may not be liable for the failure to lodge penalty at all. This is a real provision and it’s under-used. You have to ask for it: phone the ATO for amounts under $10,000, or write to them explaining the circumstances for $10,000 or more.

Payment plans

You can lodge without paying. These are two separate obligations and conflating them is the single most expensive mistake in this whole area. People hold back the lodgement because they can’t fund the payment, and end up with penalties on top of a debt they were always going to owe.

Payment plans are routinely available, and for smaller debts can often be set up online. What a plan does is stop escalating recovery action. What it doesn’t do is stop interest, which keeps accruing on the balance.

Remission

Penalties and interest can both be remitted (reduced or cancelled) on the basis of your circumstances. Serious illness, natural disaster, a systems failure, or a genuine first-time slip with an otherwise clean history are all considered. Remission isn’t automatic; it’s a request you make, in writing, setting out what happened. It’s worth making.

The order to fix it in

Sequencing matters more than speed here, and it’s not intuitive. Most people want to start at the oldest period, because that’s the one that feels worst. That’s usually the wrong end.

1. Find out exactly what’s outstanding. Not what you think is outstanding. Your ATO account lists every period and the status of each, and it’s very common for the real answer to be less bad than the assumed one.
2. Bring the current period up to date first. This stops new penalties being created while you work on the old ones, and it demonstrates good faith for any later remission request.
3. Work backwards through the outstanding periods. Since the penalty per document has already maxed out on anything more than about four months overdue, there’s no additional penalty cost to doing these in a considered order rather than a panicked one.
4. Deal with any shortfall by disclosure, before it’s found. This is where the 80% reduction lives, and it expires the moment the ATO makes contact about an examination.
5. Then sort out payment. Once the true figure is known, a payment plan can be built around a real number instead of a default assessment.

If the periods involved go back years, the substantiation side becomes the constraint rather than the lodgement side. There’s more on how that reconstruction actually works in what happens when you hand over your books for the first time, including what survives without receipts.

Where a registered agent changes the picture

Two concrete differences, beyond the obvious one of somebody else doing the work.

First, ongoing due dates get later. Eligible quarterly activity statements lodged electronically through a registered BAS agent fall under the ATO’s lodgement program, which carries concessional dates for most quarters. For 2026–27, the September quarter moved from 28 October to 25 November, the March quarter from 28 April to 26 May, and the June quarter from 28 July to 25 August. The December quarter is the exception. It already includes a one-month extension, so there’s no further concession, and its due date of 28 February 2027 falls on a Sunday, making the effective date Monday 1 March 2027.

Second, the conversation with the ATO changes character. Agents deal with the lodgement and remission process routinely, which means the request for remission or safe harbour gets framed the way the ATO expects to receive it. That’s not influence, it’s just fluency, and it matters more than it should.

If the outstanding periods need rebuilding before anything can be lodged, that’s a catch-up and clean-up, and it’s scoped separately from ongoing BAS and compliance work so the two don’t get tangled together.

The Lady Abacus takeaway

Being behind on lodgements is a bookkeeping problem, and bookkeeping problems are finite. Owing money you can’t pay is a cash flow problem, and cash flow problems are negotiable. The thing that turns both into something worse is silence, because silence is what triggers default assessments and forecloses every reduction mechanism available to you.

And the arithmetic has genuinely shifted. When interest was deductible, letting an ATO balance drift was a defensible funding decision. Since 1 July 2025 it isn’t. The debt compounds daily at a rate you now bear in full. If you’ve been carrying an old balance on the basis that the interest was effectively half price, that reasoning stopped working over a year ago.