You've just registered a new plumbing business for GST. An ATO email arrives saying your BAS is overdue, but you're still trying to work out whether the figures belong in G1, 1A, or somewhere else. The problem isn't that you're careless. BAS lodgement requirements are easy to mishandle when reporting frequency, payment deadlines, GST coding, and payroll obligations sit in different parts of the same form.
The practical answer is simple. Confirm the reporting cycle shown by the ATO, close your books before the deadline, reconcile every GST and PAYG figure, lodge the statement even when there's no activity, and pay by the applicable date. The rules below follow the ATO guidance on BAS and GST obligations, with the key recommendations I give Australian small businesses.
What a BAS Is and Who Must Lodge One
A Business Activity Statement, or BAS, is the form an Australian business uses to report and pay obligations to the ATO. Depending on the business, it can include GST, PAYG withholding, PAYG instalments, fuel tax credits, luxury car tax, wine equalisation tax, and other amounts.
GST registration creates a BAS obligation. That obligation comes from the GST framework established by the A New Tax System (Goods and Services Tax) Act 1999, so lodgement isn't an optional administrative task. You must lodge the statement for the relevant period, even if your calculation produces no amount payable.
Businesses that may need to lodge
The common categories include:
- GST-registered entities: Every business registered for GST must lodge a BAS according to its assigned reporting cycle.
- PAYG instalment businesses: An entity required to pay PAYG instalments may receive an activity statement even where its GST position differs.
- Withholding entities: A business that withholds tax from employee or other payments must report that withholding.
- Fuel-cycle participants: An entity that chooses a fuel tax credit reporting cycle may have a related obligation.
- Third parties connected with specific schemes: A third party that chooses a luxury car tax or superannuation scheme may also need to lodge.
- ATO-directed lodgers: The ATO can require an entity to lodge even where it has no GST turnover.
Sole traders, partnerships, companies, trusts, and not-for-profit organisations can all have BAS obligations. The legal structure doesn't decide the requirement by itself. Registration, withholding activity, instalment obligations, and ATO directions do.
Practical rule: A nil result is still a lodgement obligation. Don't treat an inactive quarter as a free pass.
For a new trader, the first job is to open ATO online services and identify the statement type, period, and due date. Then confirm that your bookkeeping software uses the same GST reporting basis and period. That small check prevents a common error, submitting accurate figures for the wrong cycle.
BAS Reporting Frequencies and Turnover Thresholds
The ATO assigns BAS reporting frequency primarily through GST turnover thresholds and directions, not through the business owner's preference. Your first decision is therefore not “monthly or quarterly?” It's “what cycle does the ATO currently show for this entity?”
The three reporting cycles
Monthly reporting applies when GST turnover is $20 million or more, or when the ATO directs the business to report monthly. Monthly BAS is generally due on the 21st day after the end of the reporting month. The short processing window means higher-turnover businesses need prompt invoice capture, reliable bank feeds, and disciplined GST coding.
Quarterly reporting is generally the default where GST turnover is under $20 million, unless the ATO requires monthly reporting. The standard quarters end on 30 September, 31 December, 31 March, and 30 June. Quarterly reporting suits many small businesses because it balances regular GST reconciliation with a manageable preparation workload. The ATO's threshold and reporting guidance sets out the monthly threshold and reporting rule.
Annual reporting is restricted. A business must be voluntarily registered for GST and have turnover under $75,000, or under $150,000 for a not-for-profit entity, to use annual GST reporting instead of quarterly reporting. PAYG obligations can still create separate activity-statement requirements, so annual GST reporting doesn't automatically make every obligation annual.
If you're unsure whether registration applies or how the threshold affects your position, review the GST registration threshold guidance for Australian businesses.
| Cycle | Applies when | Typical business |
|---|---|---|
| Monthly | GST turnover is $20 million or more, or the ATO directs monthly reporting | Higher-turnover entity or business under specific ATO direction |
| Quarterly | GST turnover is under $20 million and monthly reporting isn’t required | Most GST-registered small and medium businesses |
| Annual | Voluntary GST registration with turnover under $75,000, or under $150,000 for not-for-profits | Eligible low-turnover business |
Check ATO online services or the Business Portal before each new cycle. If turnover changes, don’t assume the software will update itself. Confirm the effective reporting cycle with the ATO, then update your accounting calendar, payroll timetable, and internal review date.
BAS Due Dates and Payment Deadlines
For standard quarterly BAS, use this calendar:
- 28 October: July to September quarter
- 28 February: October to December quarter
- 28 April: January to March quarter
- 28 July: April to June quarter
The ATO’s BAS due-date guidance confirms these standard dates. Check the actual statement and ATO online services because public holidays, concessions, and the statement type can affect the operative date.
Monthly lodgers generally lodge and pay by the 21st day after the reporting month. A December monthly statement falls due on 21 January, reflecting the standard monthly rule and the holiday-period timing. Monthly lodgers shouldn’t assume they receive the same concessions available to some quarterly lodgers.
Use concessions carefully
Some quarterly businesses may receive up to two extra weeks when they lodge electronically through a tax agent or the ATO Business Portal, provided the applicable eligibility conditions are met. The extension isn’t automatic for every business, and it doesn’t mean you can ignore the original date until the ATO or agent confirms the operative deadline.
Treat the due date as both a lodgement and payment deadline. Put GST collected into a separate tax holding account as invoices are paid, then ring-fence the expected amount at least one week before the deadline. That gives you time to investigate a mismatch without raiding wages or supplier funds.
Late payment can attract general interest charge, even when the BAS itself was lodged on time. Lodgement and payment are separate tasks, so schedule both in your cash-flow forecast.
Records You Must Keep to Support Your BAS
Your BAS should be the final output of a reconciled bookkeeping file, not a guess based on the bank balance. Each label needs a clear trail from the transaction to the accounting report and, if necessary, to the original document.
Sales evidence
Keep tax invoices, point-of-sale reports, receipts, credit notes, and refund records. If you issue invoices from Xero, QuickBooks, or another cloud bookkeeping system, attach the supporting document to the transaction. Refunds and credit notes deserve particular attention because they can reverse previously reported GST.
Purchase and credit evidence
Retain supplier tax invoices for purchases supporting input tax credits, together with evidence for imported goods where relevant. A claimed credit should match the purchase, the business purpose, the GST treatment, and the amount entered at the relevant BAS label.
Payroll and withholding evidence
Keep payroll reports, employee payment records, PAYG withholding summaries, contractor invoices, and voluntary withholding agreements where applicable. Reconcile the payroll report to the general ledger before entering the PAYG withholding labels. A payroll error can make an otherwise accurate GST calculation unreliable.
GST coding and retention
Review the codes behind labels such as G1, G2, G3, G10, G11, 1A, 1B, 7, and 8. The codes must reflect the transaction’s actual GST treatment, not merely the account name. GST-free sales, input-taxed transactions, capital purchases, and private-use adjustments need separate review.
Under section 262A of the Income Tax Assessment Act 1936, businesses generally need to retain relevant records for five years. Digital records can satisfy storage requirements when the business keeps them accessible, complete, and capable of being reproduced. Cloud systems help, but only if you preserve the source documents and maintain sensible user access controls.
A bank reconciliation proves where the money went. It doesn’t, by itself, prove the GST treatment.
The ATO can ask you to reconcile bank statements, invoices, payroll reports, and BAS labels. Better records reduce the chance of delayed responses, unsupported credits, and avoidable review questions.
Penalties for Late or Missing BAS Lodgement
Late BAS lodgement can cost money before you’ve even dealt with the underlying tax debt. The ATO’s failure-to-lodge framework uses one penalty unit for each 28-day period, or part period, that the statement remains overdue, up to five penalty units. For a small entity, the base amount is $330 per period under the applicable 2025-26 penalty unit value, as set out in the ATO penalty guidance.
A payable BAS can also attract a general interest charge on unpaid amounts, calculated daily and compounded. The interest continues until the underlying amount is paid or otherwise resolved, so delaying payment can increase the total cost even after lodgement.
The practical exposure
| Days late | Penalty units | Estimated cost | Plus GIC |
|---|---|---|---|
| Up to 28 days | 1 | $330 | Applies to unpaid amounts |
| 29 to 56 days | 2 | $660 | Applies to unpaid amounts |
| 57 to 84 days | 3 | $990 | Applies to unpaid amounts |
| 85 to 112 days | 4 | $1,320 | Applies to unpaid amounts |
| More than 112 days | 5 maximum | $1,650 | Applies to unpaid amounts |
The table shows the penalty-unit progression for a small entity. It doesn't replace the ATO's assessment, and larger entities can face different penalty settings.
Don't skip a nil BAS because you think no tax is owing. Lodging late is generally safer than leaving the statement outstanding, because the ATO can address the lodgement status and consider whether remission is available. Remission isn't guaranteed, so document the cause, act quickly, and contact the ATO before the deadline if genuine hardship or another serious circumstance threatens your ability to lodge or pay.
How to Prepare and Submit Your BAS Step by Step
A reliable BAS process starts well before the statement appears in ATO online services. Use the same close routine every period, and don't allow a rushed deadline to become your review system.
Close the books
- Capture source data. Enter sales, purchases, refunds, payroll, and imported goods evidence into your bookkeeping software. Attach documents and separate business transactions from private spending.
- Reconcile bank and clearing accounts. Match bank feeds, merchant settlements, loan accounts, and payroll clearing balances. Investigate unmatched items rather than forcing them into a GST code.
- Check GST treatment. Run a GST summary and exception report. Look for duplicate invoices, unusual credits, GST-free sales coded as taxable, and capital purchases posted as ordinary expenses.
- Review payroll. Match PAYG withholding reports to payroll records and the general ledger. Confirm W1 and W2 figures before you move to the BAS.
Run a trial balance after those checks. Then compare the GST totals to the source reports and investigate material changes from the previous period. A large movement isn't automatically wrong, but it needs an explanation in the working papers.
Lodge and pay
Enter the figures manually or generate them from the software, then check every populated label against the reports. DIY lodgers can use the ATO Business Portal. If a registered tax or BAS agent prepares the statement, provide complete software access and source documents before the agent's internal cut-off.
You can pay using BPAY, direct debit through the portal, or bank transfer. Use the correct payment reference and confirm when the ATO receives the payment, because the received date affects interest calculations. Save the lodged BAS, confirmation receipt, payment confirmation, and reconciliation file together.
For businesses that want an agent-prepared and agent-lodged process, EndureGo Tax's BAS lodgement service can handle bookkeeping review and BAS submission, including a same-day review where the records are ready.
Worked Example of a Quarterly BAS
Sam's Sparky Services is a hypothetical Brisbane electrical business preparing its September 2024 quarterly BAS. Sam's total sales were $88,000 including GST, including $4,000 of GST-free sales. Taxable purchases totalled $31,500 including GST, and that amount included $5,500 of capital purchases.
The labels show how the figures move through the statement:
| BAS label | Amount | Purpose |
|---|---|---|
| 1A | $80,000 | Taxable sales excluding GST |
| 1B | $4,000 | GST-free sales |
| 1C | $84,000 | Total sales reported in the example |
| 2A | $5,000 | Capital purchases excluding GST |
| 2B | $23,636 | Non-capital purchases excluding GST |
| 3 | $8,000 | GST on sales |
| 4 | $2,863 | GST on purchases |
| 5 | $5,137 | Net GST position |
| W1 | $2,400 | Total salary and wage payments |
| W2 | $nil | Amounts withheld at the relevant label |
| 7A | $7,537 | Combined amount payable in this example |
The example separates the taxable and GST-free sales so Sam can see why total deposits aren't enough to complete the BAS. 1A records taxable sales, while the GST-free amount is shown separately. The GST on sales is $8,000, and the purchase credits reduce the GST position by $2,863, leaving $5,137 at the net GST label.
Sam then adds PAYG withholding. With W1 of $2,400 and W2 showing nil, the combined 7A position is $7,537 payable. The exact treatment depends on the statement and the business's obligations, so Sam should retain the payroll report supporting those figures.
Worked-example warning: A label is only as reliable as the coding behind it. If one purchase is private, GST-free, or incorrectly treated as taxable, the result changes.
Any prior credit, adjustment, or carried-forward amount must be checked against the ATO account before Sam pays. He shouldn't blindly transfer the displayed calculation if the account contains an earlier credit or unresolved amendment.
BAS FAQs and When to Get Professional Help
Do I need to lodge a nil BAS?
Yes. If the ATO has issued a BAS or you have an active lodgement obligation, you must lodge it by the due date even when the business made no sales, claimed no credits, and owes no GST. Seasonal traders and newly registered businesses are particularly likely to miss this because they confuse “no activity” with “no obligation”.
Can I change my BAS reporting cycle?
You can request a change through Access Manager or by phoning the ATO on 13 28 66 before the next cycle starts. Don't change only the software setting. The ATO account must show the correct cycle, otherwise you can create missing statements or duplicate reporting.
Can I switch from DIY lodgement to a tax agent?
Yes. Engage a registered tax or BAS agent, provide authority and bookkeeping access, and give the agent the complete working papers. The agent can then prepare and lodge future statements through the authorised channel. You remain responsible for providing accurate records and checking that the arrangement covers every relevant entity.
Must a BAS agent be registered?
Yes. A person providing BAS services for a fee generally needs registration under the Tax Agent Services Act 2009. Ask for the agent's registration details before handing over access to payroll, bank feeds, or ATO online services.
How long will ATO correspondence take?
The timing depends on the type of correspondence, the issue, and the ATO's processing workload. Keep checking ATO online services and respond by the stated date. Escalate when a deadline is approaching, a refund is delayed without explanation, or repeated contact has not resolved the issue.
When should I get professional help?
Call a registered professional when payroll is messy, several entities share transactions, the business has $500,000-plus turnover, or repeated late lodgements show that the current process isn't working. EndureGo Tax provides bookkeeping and BAS lodgement support, including reconciliation work and compliant ATO-portal lodgement.
EndureGo Tax can organise your bookkeeping, reconcile GST and payroll records, prepare your BAS, and lodge it through the compliant ATO channel. Visit EndureGo Tax to arrange a review before your next BAS deadline, particularly if missed lodgements or inconsistent GST coding are already causing stress.
