Every quarter, thousands of Australian business owners open a shoebox of receipts three days before the deadline and hope for the best. It works, right up until the quarter it does not.
BAS is not difficult. It is just unforgiving about two things: accuracy and timing. Get those right and lodgment becomes a twenty-minute admin job instead of a weekend.
The four practices below are the ones that separate the businesses who dread BAS from the ones who barely notice it.
Key Takeaways:
- Quarterly BAS is due on 28 October, 28 February, 28 April and 28 July. Lodging through a registered agent buys you roughly four extra weeks on three of those four quarters.
- Late lodgment costs one penalty unit per 28 days overdue, capped at five units for small entities. From 1 July 2026, a penalty unit is $364, so a maxed-out penalty is $1,820 per statement.
- Reconciling weekly instead of quarterly is the single biggest reducer of BAS stress and BAS errors.
- Most GST mistakes cluster in the same handful of transactions: bank fees, insurance, government charges, food and vehicle purchases.
- You need a valid tax invoice to claim a GST credit on any purchase over $82.50 including GST, and records must be kept for five years.
1. Know your cycle, then work backwards from the real deadline
Your reporting cycle is set by turnover. Businesses under $20 million generally report quarterly, those at $20 million or more report monthly, and some voluntarily registered businesses under the $75,000 threshold can report annually.
For quarterly lodgers, the dates are fixed and predictable. The July to September quarter is due 28 October, October to December is due 28 February, January to March is due 28 April, and April to June is due 28 July. Monthly lodgers are due on the 21st of the following month.
Here is the part many owners miss. If you lodge through a registered tax or BAS agent, the ATO’s lodgment program generally gives you about four extra weeks on quarters one, three and four. Quarter two gets no extension because the 28 February date already accounts for the Christmas break.
The cost of getting this wrong is mechanical rather than discretionary. A failure to lodge penalty accrues at one penalty unit for every 28 days or part thereof that the statement is overdue, capped at five units for small entities with turnover under $1 million. At $364 per unit from 1 July 2026, a statement three months late costs $1,456.
If you know you cannot lodge in time, contact the ATO before the due date rather than after. Payment plans and deferrals exist, but they are far easier to arrange while the statement is still current.
2. Prepare across the quarter instead of the night before
The single practice that changes BAS most is boring: reconcile weekly. Fifteen minutes every Friday beats six hours on 27 October, and it catches problems while you still remember the transaction.
Weekly reconciliation also protects your cash flow. When your GST position is current, you know roughly what you owe at any point in the quarter, which means the payment is a planned expense rather than a nasty surprise.
This is the job modern accounting software is genuinely good at. MYOB’s AI BAS tool, for example, works progressively across the quarter and automates the grunt work by suggesting categories for uncategorised BAS-relevant transactions, flagging GST anomalies and surfacing missing expense documents for items over $82.50 as they happen.
The design choice worth noting is that nothing changes without you approving it. Each suggestion comes with a plain-English explanation; you accept, edit, or reject it, and approved decisions flow straight through to your books so the ledger and the BAS never drift apart.
A readiness dashboard tracks how close you are to lodgment, which turns the quarter into a visible progress bar rather than a cliff. Worth knowing before you rely on it: the tool prepares your BAS but does not lodge it with the ATO, and MYOB is not a registered tax or BAS agent, so you or your agent still enter the figures and submit.
Whatever software you use, the principle holds. Data entered close to the transaction is more accurate than data reconstructed from a bank statement three months later.
3. Get the GST coding right on the transactions that trip everyone up
Most GST errors are not exotic. They cluster in a predictable handful of transactions that people code on autopilot.
Bank fees and interest are input taxed, so there is no GST to claim. Most basic food, many health services and some education courses are GST-free. Government charges such as council rates, land tax and most ASIC fees carry no GST either.
Then there is the mixed-purpose problem. If you buy a laptop and use it 70 percent for business, you claim 70 percent of the GST credit, not the lot. The same logic applies to a vehicle, a phone plan or a home internet connection.
Two more worth watching. Purchases from suppliers who are not registered for GST have no GST component even if the invoice looks like a normal one, so check the ABN. And overseas digital subscriptions may or may not include Australian GST depending on how the supplier is registered.
If you have made an error in a previous statement, you do not always need a formal amendment. The ATO allows many small GST mistakes to be corrected on a later BAS, within value and time limits set by turnover, which is far simpler than revising the original.
4. Build a paper trail you could hand to an auditor tomorrow
Records are where good intentions quietly fall apart. The rule is simple: keep your business records for five years from when you prepared or obtained the record, or completed the transaction it relates to, whichever is later, and keep them in a form the ATO can access and read.
For GST credits specifically, you need a valid tax invoice for any purchase over $82.50 including GST. Under that amount, a receipt or bank statement entry will usually do, but a tax invoice is still the safer habit.
A valid tax invoice has to show the supplier’s identity and ABN, the date, a description of what was supplied, the GST amount or a statement that the total includes GST, and the buyer’s identity for invoices of $1,000 or more. Photograph receipts at the point of purchase, because thermal paper fades and a faded receipt is not much use.
It also pays to keep the working, not just the answer. Save the reconciliation report or BAS summary that supports each lodged statement, so that if a figure is queried in two years you can show how you arrived at it rather than rebuilding it from scratch. This is also where most common BAS mistakes are caught, well before the ATO ever sees them.
One last habit. Reconcile your BAS figures back to your profit and loss and your bank balance before you lodge. If the three do not agree, the problem is in your books rather than your statement, and it is much cheaper to find it now.
Bringing it together
None of this requires an accounting degree. It requires a cycle you understand, a weekly habit, care on a dozen transaction types, and records you can actually produce.
Do those four things, and BAS stops being a quarterly emergency. It becomes what it was always meant to be, which is a short summary of what your books already say.
FAQ
1. When is my BAS due?
Quarterly BAS is due on 28 October, 28 February, 28 April and 28 July. Monthly BAS is due on the 21st of the following month. If the date falls on a weekend or public holiday, it usually moves to the next business day.
2. What happens if I lodge my BAS late?
The ATO may apply a failure to lodge penalty of one penalty unit for each 28-day period the statement is overdue, capped at five units for small entities. A general interest charge can also apply to any unpaid amount.
3. Do I get extra time if I use a BAS agent?
Usually yes. The ATO’s lodgment program gives registered agents roughly four extra weeks for quarters one, three and four. Quarter two keeps its 28 February date.
4. Can accounting software lodge my BAS for me?
Some platforms lodge directly, and others prepare the figures for you or your agent to submit. Check what your specific product does before you assume the lodgment step is covered.
5. How long do I need to keep BAS records?
Five years, counted from when you prepared or obtained the record or completed the transaction it relates to, whichever is later. Records need to be in English or easily translatable, and stored in a way you can retrieve if the ATO asks.
6. Can I fix a GST mistake from a previous quarter?
Often yes. The ATO lets many small GST errors be corrected on a later BAS rather than by amending the original, subject to value and time limits based on your turnover.