Let us start with the reassuring bit, because if you are reading this you probably need it: being behind on your BAS is fixable, it is more common than you think, and it is almost always less catastrophic than the story running in your head at 2am. What it is not is something that fixes itself. The penalties compound, the interest ticks daily, and Barry, who got you here, is currently hiding behind a pot plant hoping you do not open the ATO portal.

Published: July 2026

First, breathe. Then understand what you are dealing with

There are two clocks running when a BAS is overdue, and it helps to separate them.

The first is the failure-to-lodge penalty, which is about not lodging on time. The second is the General Interest Charge, which is about not paying on time. They are different things with different fixes, and knowing which one you are facing changes what you do first. The single most important move, and the one Barry never makes, is to lodge, even if you cannot pay. Lodging stops the failure-to-lodge clock, and ongoing BAS lodgement done on time means you never face this clock again. Paying is a separate conversation you can have with the ATO afterwards, including payment plans.

If your books are too far gone to even prepare a BAS, that is not a dead end, that is a books catch-up job, and it is a big part of what we do.

The real penalty maths (so you can stop guessing)

Vague dread is worse than real numbers, so here are the real numbers.

The failure-to-lodge penalty is built on the Commonwealth penalty unit, which rose to $364 on 1 July 2026. For a small business, the ATO charges one penalty unit for each 28-day period (or part of one) that the statement is overdue, capped at five periods. So the maximum failure-to-lodge penalty on a single late BAS is 5 x $364 = $1,820. A statement that is 29 days late has ticked into a second period, so it attracts two units, not one. The “part of a period counts as a whole period” rule is how these add up faster than people expect.

Then there is the interest. If you owe money and have not paid, the General Interest Charge applies daily from the original due date. For the July to September 2026 quarter it sits at roughly 11.43% a year, compounding daily. And here is the part that quietly changed the maths: since 1 July 2025, that interest is no longer tax deductible. It used to be softened by a deduction. Now every dollar of ATO interest is a pure cost, and at over 11% it is dearer than most business loans.

Stack it up on, say, three overdue quarterly statements with tax owing, and you can be looking at low-thousands in failure-to-lodge penalties before you have paid a cent of interest or the actual GST. That is the cost of leaving it. It is also entirely avoidable from here, and knowing your next BAS due date is step one.

The catch-up sequence (how a rescue actually runs)

A proper BAS rescue is not chaos. It is a sequence, and running it in order is what keeps the damage contained.

1. Damage assessment. Work out exactly which statements are outstanding, for which periods, and whether tax is owing or a refund is due on each. You cannot fix what you have not measured. Sometimes an overdue BAS is actually in refund, which changes the whole picture.
2. Reconcile the underlying books. You cannot lodge an accurate BAS off a Xero file nobody has touched in months. This is usually the bulk of the work: bringing the bank reconciliations up to date, sorting the GST coding, cleaning up the mess that caused the backlog in the first place. If the file is a genuine disaster, this is where a Xero file cleanup comes in.
3. Lodge, oldest first. Get the statements in. Oldest first stops the penalty periods stacking any further and shows the ATO you are actively fixing it, which matters for the next step.
4. Request remission. Once the overdue statements are lodged (and the ATO will not even consider this until they are), you can apply to have failure-to-lodge penalties reduced or waived, especially if you have an otherwise clean history or there were genuine circumstances behind the delay. This step alone can wipe a meaningful chunk of the penalty, and it is one Barry never bothers with.
5. Set up so it never happens again. A rebuilt compliance calendar, weekly reconciliation, and a fixed-price bookkeeping package so BAS is just handled. The whole point is that this is the last rescue you ever need.

The registered agent breathing room most owners do not know about

Here is a genuine advantage of moving to a bookkeeper who lodges through the registered agent program. Agents get concessional lodgement dates that are later than the standard self-lodged deadline. The September 2026 quarter BAS, for example, is due 28 October if you lodge it yourself, but an agent’s concessional date runs later. That extra window is not a loophole, it is a legitimate part of how the system is built, and it can be the difference between scrambling and getting it done properly. It is one of the quiet reasons switching to the right bookkeeper pays for itself.

The honest bit about staying with Barry

You might be tempted to let the current bookkeeper “sort it out”. Consider how you got here. A bookkeeper who let three BAS statements go overdue without raising the alarm is not going to suddenly become the person who runs a clean rescue and negotiates a remission. The behaviour that created the backlog is the behaviour you would be trusting to fix it. If that is landing a bit close to home, our guide on how to change bookkeepers walks through doing it cleanly, even mid-mess.

FAQ

Should I lodge my BAS even if I cannot pay it?
Yes. Lodging stops the failure-to-lodge penalty clock. Paying is a separate issue, and the ATO offers payment plans. Not lodging because you cannot pay is the most expensive mistake, because it leaves both clocks running.

How much is the penalty for a late BAS?
For a small business, it is one penalty unit ($364 from 1 July 2026) for each 28-day period the statement is overdue, up to a maximum of five periods, so $1,820 per late statement at most. Interest on unpaid amounts is separate and accrues daily.

Can late BAS penalties be reduced or waived?
Often, yes. You can request remission once the overdue statements are lodged. A clean prior history and genuine reasons for the delay help. The ATO will not consider remission until the outstanding statements are actually in.

How far back can I catch up?
As far back as needed. A rescue engagement works through all outstanding periods, reconciling the books for each before lodging. Older backlogs take more work but are still fixable.

What is the General Interest Charge and is it deductible?
It is the daily interest the ATO charges on unpaid amounts, 11.43% a year for the July-September 2026 quarter (rates reset quarterly) and compounding daily. Since 1 July 2025 it is no longer tax deductible, which makes carrying an ATO debt more expensive than it used to be.

Will moving to a registered agent give me more time?
Registered agents have concessional lodgement dates that are later than standard self-lodged deadlines. Moving to a bookkeeper who lodges through the agent program can give you legitimate extra breathing room on future statements.

How long does a BAS rescue take?
It depends on how far behind the books are. Reconciling the underlying file is usually the bulk of the work. Once that is done, lodging and requesting remission move quickly.

About Sydney Bookkeeper

Sydney Bookkeeper is the modern, fixed-price Sydney bookkeeper for businesses with staff that are tired of slow, hourly, jargon-spouting incumbents. We work with professional services firms, construction and property businesses, agencies, tech and ecommerce companies, hospitality groups, and health practices across Sydney. Monthly bookkeeping, BAS lodgement, payroll, and Xero file cleanups, all on fixed monthly pricing, no lock-in.

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The team uses a registered BAS Agent for all BAS and IAS lodgement services. Full registration details, agent particulars, and copies of the Tax Practitioners Board (TPB) Code of Professional Conduct, the TPB complaints process, and any conditions on the agent’s registration are available on request by emailing [contact email]. This content is general information only, written for Australian small and mid-market businesses. It does not constitute tax, financial product, or legal advice and should not be relied on as such. Penalty and remission outcomes depend on your individual circumstances. For advice specific to your business, contact the team directly or consult a registered tax agent or the ATO. Sydney Bookkeeper is not a licensed tax agent or licensed financial adviser. Information was current at the time of publication and may change without notice. We review and update guides periodically.

Sources

• Australian Taxation Office, Failure to lodge on time penalty: https://www.ato.gov.au/individuals-and-families/paying-the-ato/interest-and-penalties/penalties/failure-to-lodge-on-time-penalty
• Australian Taxation Office, Penalty units: https://www.ato.gov.au/individuals-and-families/paying-the-ato/interest-and-penalties/penalties/penalty-units