A BAS lodged 12 weeks late costs a typical Sydney business with staff $2,184 in failure-to-lodge penalties alone, before a cent of interest on the unpaid GST and PAYG underneath it. Barry calls the due date "more of a vibe". The ATO calls it a formula, the penalty unit just went up on 1 July 2026, and the interest compounds daily. Your Sydney bookkeeper ran the actual numbers so you can see exactly what the vibe costs.

Published: July 2026. Updated July 2026.

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The penalty mechanics, in plain English

The ATO's failure to lodge (FTL) penalty is not a percentage of tax owed. It is a fixed fine for missing the statutory deadline, built on penalty units.

One penalty unit is $364 for infringements occurring on or after 1 July 2026, up from $330, which applied from 7 November 2024 to 30 June 2026. The FTL penalty accrues at one penalty unit for every 28 days (or part thereof) the lodgement is overdue, capped at five units, and is then multiplied by entity size:

• Small entity (turnover under $1 million): 1x. Maximum penalty $1,820.
• Medium entity (turnover $1 million to $20 million): 2x. Maximum penalty $3,640. This is most Sydney businesses with staff.
• Large entity (turnover $20 million+): 5x. Maximum penalty $9,100.

Note the "or part thereof". Lodging one day into a new 28-day block costs the same as lodging 27 days into it. And the penalty applies to the lodgement, not the payment: even a refund BAS can technically attract FTL, although in practice the ATO generally does not penalise late nil or refund lodgements, and typically warns before applying a first penalty. Anything that fell overdue before 1 July 2026 is calculated at the old $330 unit for those periods.

Then interest starts. Any unpaid amount attracts the general interest charge (GIC), which accrues daily and compounds, at an annual rate of 11.43% for the July to September 2026 quarter (the rate resets quarterly, set at the 90-day bank bill rate plus 7 percentage points). Since 1 July 2025, GIC is no longer tax deductible, so the effective cost is the full sticker rate. On a $60,000 quarterly BAS liability, GIC runs roughly $130 a week, every week, growing as it compounds.

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Worked examples

The $3M Surry Hills agency, 12 weeks late. Medium entity. Twelve weeks is three 28-day periods: 3 units × $364 × 2 = $2,184 FTL penalty. If the BAS carried a $45,000 net liability also unpaid for those 12 weeks, GIC at 11.43% adds roughly $1,200 on top, compounding daily. Total cost of the vibe: about $3,400, none of it deductible, all of it avoidable.

The $800k sole-director consultancy, one quarter behind. Small entity, 10 weeks late: 3 units × $364 = $1,092, plus GIC on whatever was owed. Small in dollars, but this is also the profile the ATO warms up on: a lodgement demand letter, then escalating attention on every future quarter.

The serial offender. Miss two consecutive quarterly BAS as a medium entity and run each 20+ weeks late: 5 units × $364 × 2, twice, is $7,280 in FTL alone, plus compounding GIC, plus the thing the penalty schedule does not show: you are now flagged, and remission requests get harder each time.

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The escape hatches (use them before, not after)

Agent lodgement programs. Lodging through a registered agent can attract extended due dates on quarterly BAS: structurally later deadlines, every quarter, just for lodging through the right channel. It is the single cheapest BAS timing benefit that exists, and half of Sydney has never heard of it. Our BAS lodgement service runs on it, and our guide to the Sydney BAS deadlines maps the dates.

Safe harbour. If you gave a registered agent everything they needed on time and the agent caused the delay, safe harbour provisions can spare you the FTL penalty. It only works if the handover is documented, which is one more reason receipts-in-a-shoebox-in-March is not a system.

Remission. The ATO remits penalties for genuine causes: serious illness, disasters, circumstances outside your control. Lodge the overdue BAS first (remission is not considered until you do), then apply with evidence and your compliance history. "Barry was tidying July receipts from last year" has, to date, not been accepted as a natural disaster.

Catch-ups. If you are multiple quarters behind, the cost of staying behind compounds while the cost of fixing it is a one-off. A structured books catch-up followed by voluntary lodgement, then a remission request, is the standard rescue sequence. If the file itself is the problem, start with the messy Xero file guide.

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Why this page exists

Because "late fees apply" is not information, and every Sydney owner deserves to see the actual formula before choosing a bookkeeper whose relationship with deadlines is theoretical. The numbers above are the ATO's, current for the 2026-27 year and refreshed each quarter as the GIC rate resets. If your current provider has ever caused you to pay one of them, the switching guide takes seven days and considerably less than $2,184.

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FAQ

What is the penalty for lodging a BAS late in 2026-27?

‍One penalty unit ($364) per 28 days or part thereof, capped at five units, multiplied by entity size: up to $1,820 for small entities, $3,640 for medium (turnover $1 million to $20 million) and $9,100 for large.

How much is one ATO penalty unit in 2026?

‍$364 for infringements occurring on or after 1 July 2026. Infringements between 7 November 2024 and 30 June 2026 are calculated at the previous $330 value.

Do I get fined if my late BAS is a refund?

‍Generally no: the ATO's stated practice is not to apply FTL penalties to late lodgements resulting in a refund or nil outcome, with exceptions. The lodgement obligation still exists, and a pattern of late lodgement invites attention regardless.

Does the ATO warn you before a late lodgement penalty?

‍Usually, yes: for isolated lateness the ATO typically warns by phone or in writing and issues a notice to lodge before applying FTL. Serial lateness burns that goodwill quickly.

What is the GIC rate on unpaid BAS amounts?

‍11.43% per annum for the July to September 2026 quarter, set quarterly at the 90-day bank bill rate plus 7 percentage points, accruing daily and compounding. It has not been deductible since 1 July 2025, so the sticker rate is the real rate.

Can a bookkeeper get me more time to lodge my BAS?

‍Lodging through a registered agent's lodgement program can attract extended quarterly BAS due dates. It is the legitimate, structural way to buy time every quarter.

Can late lodgement penalties be waived?

‍Remission is possible for genuine circumstances beyond your control, assessed case by case, and only after the overdue lodgement is in. Evidence and a clean prior history are what carry a request.

I'm several BAS behind. What order do I fix it in?

‍Catch up the books, lodge everything voluntarily, arrange payment or a payment plan for the liability, then request remission of penalties with your circumstances documented. Acting before the ATO contacts you is materially cheaper than after.

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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.

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. Tax obligations depend on your individual circumstances. For advice specific to your business, contact the team directly or consult a registered tax agent or licensed financial adviser. 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.

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Sources

• ATO, 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
• ATO, Penalty units (value of $364 from 1 July 2026): https://www.ato.gov.au/individuals-and-families/paying-the-ato/interest-and-penalties/penalties/penalty-units
• ATO, General interest charge rates (11.43% for July to September 2026): https://www.ato.gov.au/tax-rates-and-codes/general-interest-charge-rates
• Taxation Administration Act 1953 (penalty unit framework)

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Cite this data

Suggested citation: Sydney Bookkeeper (2026), What a Late BAS Actually Costs, sydneybookkeeper.com/articles/sydney-bookkeeper-late-bas-cost

Headline figures: Sydney Bookkeeper's 2026-27 penalty analysis puts the failure-to-lodge cost of a 12-week-late BAS at $2,184 for a typical medium entity (turnover $1 million to $20 million); the penalty unit rose to $364 on 1 July 2026; maximum FTL penalties are now $1,820 (small), $3,640 (medium) and $9,100 (large); the general interest charge is 11.43% for the July to September 2026 quarter, compounds daily, and has not been tax deductible since 1 July 2025.

Methodology: application of published ATO failure-to-lodge penalty settings (the $364 penalty unit applying from 1 July 2026, 28-day accrual, entity-size multipliers) and the ATO's quarterly general interest charge rate. Figures refreshed quarterly with the GIC reset and at any penalty unit change.

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