AU BAS Quarter Guide FY2026–27: Due Dates, G1, 1A and 1B, and How Offshore Accounting Helps
A BAS quarter is a three-month GST reporting period. In FY2026–27, the quarters end 30 September, 31 December, 31 March and 30 June, and lodgement is due 28 October, 1 March, 28 April and 28 July. This guide explains those dates and the G1, 1A and 1B labels. It also shows how an offshore accounting team can prepare the reconciliations, GST coding and BAS data each quarter, while a registered tax or BAS agent reviews and lodges the statement.
Key Takeaways
BAS quarters follow the financial year. FY2026–27 quarters end 30 September, 31 December, 31 March and 30 June.
The due dates are 28 October 2026, 1 March 2027, 28 April 2027 and 28 July 2027. Q2 shifts to 1 March because 28 February falls on a Sunday.
Net GST equals 1A minus 1B. A positive result is payable to the ATO, and a negative result is a refund.
Most small businesses report three GST labels. Under $10 million GST turnover, Simpler BAS asks for G1, 1A and 1B.
Tax invoices matter. Purchases over $82.50 including GST need a valid tax invoice before you claim the credit.
An offshore team can prepare the BAS workings (reconciliations, GST coding, invoice checks and draft 1A and 1B figures), while a registered tax or BAS agent reviews and lodges.
Your own statement has the final say on dates. Concessions for online and agent lodgers carry conditions.
What Is a BAS Quarter?
A BAS quarter is the three-month period you report on your Business Activity Statement, and quarters follow the financial year, so Quarter 1 always starts on 1 July. Once your GST turnover reaches $75,000 you need to register for GST, and from that point the BAS becomes a regular part of running the business.
Many small businesses report quarterly, while others report monthly, with each monthly statement due on the 21st of the following month. Your activity statement shows which cycle applies to you.
BAS Quarter Dates for FY2026–27
The ATO's BAS agent lodgment program for 2026–27 sets the standard dates, and the table below adds the extra time some lodgers can get.
Quarter | Period | Standard due date | Online lodger, if eligible (indicative) | Registered agent, if eligible |
Q1 | 1 Jul to 30 Sep 2026 | 28 Oct 2026 | 11 Nov 2026 | 25 Nov 2026 |
Q2 | 1 Oct to 31 Dec 2026 | 1 Mar 2027 | No extra time | No concession |
Q3 | 1 Jan to 31 Mar 2027 | 28 Apr 2027 | 12 May 2027 | 26 May 2027 |
Q4 | 1 Apr to 30 Jun 2027 | 28 Jul 2027 | 11 Aug 2027 | 25 Aug 2027 (provisional) |
A few details sit behind those dates:
Q2 moves to Monday 1 March 2027: The ATO lists 28 February 2027, which falls on a Sunday, so lodgement rolls to the next business day.
Online lodgers may get two extra weeks: The ATO says quarterly lodgers who receive and lodge online may receive an additional two weeks for Quarters 1, 3 and 4. Quarter 2 lodgers already have eight weeks, so no extra time applies. Treat the online dates as indicative and follow your own statement.
Agent concessions come with conditions: The dates apply when a registered agent lodges electronically and the client's previous statement was also lodged electronically. A first statement, or one that followed a paper lodgement, may carry an earlier date.
The Q4 agent date is provisional: The ATO lists 25 August 2027 as to be confirmed when the 2027–28 program is developed.
Payment is due with lodgement: The ATO's guidance is to lodge and pay in full by the due date.
The One-Line Maths Behind Every BAS
Net GST equals 1A minus 1B. If 1A (the GST you collected on sales) is higher than 1B (the GST you can claim on purchases), you pay the difference to the ATO. If 1B is higher, the ATO owes you a refund.
Every other GST label exists to get you to those two numbers.
G1, 1A and 1B Explained
G1, Total sales: This covers all sales for the quarter, including GST-free and input-taxed sales. You can report G1 including or excluding GST, and you indicate your choice on the statement. The cheat sheet at the end of this guide works with GST-inclusive amounts, which keeps the 1A calculation to a simple division by 11.
1A, GST on sales: This is the GST you owe on your taxable sales. For taxable sales at 10% that include GST, divide the amount by 11.
1B, GST on purchases: These are the GST credits you can claim on business purchases. Purchases over $82.50 including GST need a valid tax invoice before you claim, according to the ATO, and where an invoice only says the price includes GST, you divide the price by 11 to find the credit.
Most small businesses only report these three labels. If your GST turnover is under $10 million, Simpler BAS is the default reporting method, and the ATO says it lets you skip the GST calculation worksheet and the sales and purchase categories. At $10 million or more, full reporting applies and asks for more labels.
The Supporting Labels and Where They Fit
The remaining labels help you work out 1A and 1B from your accounting records, and they follow the ATO's GST calculation worksheet. The cheat sheet's calculator uses the same steps, so all of these sit on one page.
Label | What it covers |
G2 | Export sales (GST-free) |
G3 | Other GST-free sales, such as many basic foods and certain health and education supplies |
G4 | Input-taxed sales, such as residential rent and financial supplies, with no GST charged and no credits on related costs |
G10 | Capital purchases such as equipment, vehicles and fit-out, including GST |
G11 | Non-capital purchases such as everyday expenses and stock, including GST |
G13 to G15 | Purchases with no GST credit: G13 for input-taxed sales, G14 where the price has no GST, G15 for private use |
W1 and W2 | Gross wages and PAYG withheld, which apply only if you withhold tax from employees and sit outside GST |
8A, 8B and 9 | The BAS summary: 8A is what you owe, 8B is what the ATO owes you, and 9 is the payment or refund |
A Worked Example
Here is the calculation using the illustrative figures from the cheat sheet's example column. They are sample numbers only.
Step | Label | Amount |
Total sales, including GST | G1 | $110,000 |
Less GST-free sales | G3 | $5,500 |
Taxable sales, including GST | G6 | $104,500 |
GST on sales (÷ 11) | 1A | $9,500.00 |
Capital purchases | G10 | $11,000 |
Non-capital purchases | G11 | $38,500 |
Less purchases with no GST in the price | G14 | $6,000 |
Purchases with GST credits | G17 | $43,500 |
GST on purchases (÷ 11) | 1B | $3,954.55 |
Net GST (1A − 1B) | $5,545.45 payable to the ATO |
A Quarter-End Routine That Avoids the Scramble
Spreading the work across the weeks after quarter end keeps the last few days before the due date calm. Here is a routine that works for most businesses:
Week 1
Freeze the period and note whether you report on a cash or accruals basis.
Reconcile every bank and card account for the quarter.
Review sales for correct GST codes (taxable, GST-free, input-taxed, export).
Check purchases against tax invoices and fix any wrong GST codes.
Week 2
Separate capital purchases (G10) from everyday expenses (G11).
Remove private use and other items with no GST credit.
Run the GST report and work out 1A and 1B.
Compare 1A and 1B with last quarter, and investigate any large swing.
Before the due date
If you withhold tax from employees, match W1 and W2 to your Single Touch Payroll reports.
Lodge the BAS and save the receipt number.
Pay by the due date, or arrange a payment plan with the ATO early.
File the BAS, worksheet and supporting records for at least five years.
Common BAS Quarter Mistakes
Swapping labels: G1 is a sales total, while 1A and 1B are GST amounts.
Claiming 1B without a tax invoice: For purchases over $82.50 including GST, the ATO says to wait until you hold the invoice, even if it arrives in a later period.
Putting a transaction in the wrong quarter: Your accounting basis, cash or accruals, decides where a sale or purchase lands.
Treating wages and super as GST purchases: They stay out of G11.
Missing the Q2 date shift: The December quarter falls due on Monday 1 March 2027, not 28 February.
Relying on a guide over your own statement: Your activity statement shows your actual due date, and it prevails if it differs from any published calendar.
How Does an Offshore Accounting Team Help Prepare Your BAS Each Quarter?
An offshore accounting team takes on the preparation work that fills the weeks after each quarter ends: reconciling accounts, checking GST codes, matching purchases to tax invoices and compiling the figures behind 1A and 1B. A registered tax or BAS agent then reviews the figures and lodges the statement.
That split gives your local team more time to review and less time chasing data, which is where most last-minute BAS stress comes from.
Quarter-end step | What the offshore team prepares | What stays with the registered agent or local team |
Reconcile bank and card accounts | Reconciles every account for the quarter and flags unmatched items | Answers queries only the business can answer |
Review GST codes | Checks taxable, GST-free, input-taxed and export codes and corrects clear miscodes | Decides treatment for unusual or high-value transactions |
Check purchases against tax invoices | Matches purchases over $82.50 including GST to valid tax invoices and lists any that are missing | Decides whether a credit can be claimed where an invoice is missing |
Split capital (G10) from non-capital (G11) purchases | Prepares the split and flags private-use items | Confirms the treatment |
Work out 1A and 1B | Compiles the GST report and draft figures, compares them with last quarter and notes large swings | Reviews the figures and approves them |
Match W1 and W2 to payroll reports | Prepares the reconciliation of wages and PAYG withheld to Single Touch Payroll reports | Reviews any variances |
Lodge and pay | Not part of the offshore role | Registered agent lodges, and the business pays by the due date or arranges a payment plan |
Keep records | Organises the BAS, worksheet and supporting records in the file | Retains them for at least five years |
In practice, this changes four things about the quarter-end routine:
Reconciliations finish in week one: The team works in your Xero, MYOB or QuickBooks file during Australian business hours, so the work starts as soon as the quarter closes.
GST miscoding is caught before it reaches the BAS: A wrong code on a sale or purchase flows straight into 1A or 1B, so checking codes early protects the net GST figure.
Missing tax invoices are listed early: That leaves time to chase suppliers before the due date, rather than losing a credit.
Your reviewer starts from a draft, not raw data: The registered agent receives workings with variance notes against the previous quarter, which makes the review faster and easier to document.
The boundary matters. The offshore team prepares, and the registered tax or BAS agent lodges, which keeps lodgement where Tax Practitioners Board rules require it. Agree upfront who owns each step, so nothing falls between the two teams in the final week.
What Happens If You Lodge Late?
The ATO may apply a failure to lodge on time penalty of one penalty unit, $364 from 1 July 2026, for each 28 days or part of 28 days a statement is overdue. For a small entity the penalty is capped at five units, or $1,820, and higher multiples apply to medium and large entities. General interest charge also accrues on unpaid amounts.
If you can't lodge or pay on time, contact the ATO early, and remember that a nil BAS still needs lodging by the due date.
Conclusion
A BAS quarter becomes manageable once you know the four dates, the three labels and the one-line maths that connects them. Reconcile early, check your GST codes and tax invoices, and compare 1A and 1B with the previous quarter before you lodge.
Where the preparation work keeps stacking up, an offshore accounting team can handle the reconciliations and GST coding, so your registered agent can review and lodge with time to spare. That routine turns each due date into a calm, repeatable task instead of a last-minute rush.
Getting the BAS Ready Without the Quarterly Scramble
If reconciliations and GST coding keep stacking up before each due date, BOS Resources can prepare that work for you.
Team members bring a minimum of one year's direct experience working with Australian businesses and work Australian business hours. Our guide to offshoring GST compliance covers the split between preparation and lodgement in more detail.
Download the AU BAS Quarter Cheat Sheet (FY26–27)
Want the dates, labels and calculations on one page? The cheat sheet is a free workbook with five tabs:
Cheat Sheet: G1, 1A and 1B explained, the one-line maths, a FY2026–27 quarter map and the common traps
Due Dates: quarterly and monthly due dates, agent concession dates and a status tracker, with a days-to-due counter that turns amber within 14 days and red when overdue
BAS Calculator: enter GST-inclusive sales and purchases by quarter, and it works through to 1A, 1B and net GST with built-in checks
Checklist: the 12-step quarter-end routine with a progress percentage for each quarter
Notes & Sources: where the dates come from, plus assumptions and a disclaimer
The calculator assumes standard 10% GST, so margin scheme and other special schemes need advice from a registered tax or BAS agent. If you'd like help getting your books BAS-ready each quarter, get in touch with BOS Resources.
This guide and the cheat sheet are general information only and not tax advice. Confirm dates and treatment with the ATO or a registered tax or BAS agent.
Frequently Asked Questions
When are BAS quarters due in FY2026–27?
Quarterly BAS statements are due on 28 October 2026, 1 March 2027, 28 April 2027 and 28 July 2027. The Quarter 2 date is listed as 28 February 2027, which falls on a Sunday, so lodgement rolls to Monday 1 March. Eligible online and agent lodgers may get extra time for Quarters 1, 3 and 4.
What do G1, 1A and 1B mean on a BAS?
G1 is your total sales for the period. 1A is the GST you collected on taxable sales, and 1B is the GST credits you can claim on business purchases. Net GST is 1A minus 1B: a positive result is payable to the ATO, and a negative result is a refund.
Do I need to complete every G label on my BAS?
Only businesses with GST turnover of $10 million or more must use full reporting. Under $10 million, Simpler BAS is the default and asks for just G1, 1A and 1B, with no GST calculation worksheet. The other labels remain useful as workings for reaching 1A and 1B.
What is the penalty for lodging a BAS late?
The ATO may apply one penalty unit, $364 from 1 July 2026, for each 28 days or part of 28 days a statement is overdue. A small entity's penalty is capped at five units, or $1,820. General interest charge applies separately to unpaid amounts.
Can an offshore accounting team lodge my BAS?
No. The offshore team prepares reconciliations, GST coding and BAS data, and a registered tax or BAS agent reviews and lodges the statement. This keeps lodgement where Tax Practitioners Board rules require it.
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