September Quarter BAS Checklist for Agent-Lodged Businesses

If a registered tax or BAS agent lodges your September quarter (July to September 2026) BAS electronically, the ATO's lodgment program due date to lodge and pay is 25 November 2026. The standard due date was 28 October 2026; the later date applies when your agent lodges electronically and your previous activity statement was also lodged electronically. As at 9 November 2026 that leaves about two and a half weeks, so this is the window to get the figures underneath the BAS right.

Your agent lodges. Your part is handing over figures clean enough to lodge without back and forth: a bank feed that ties out, private spending lifted out, and every line under the right GST treatment. This checklist works through those in the order that saves the most time.

Key takeaways

• Agent-lodged, electronic: the September quarter 2026-27 BAS is due 25 November 2026 to lodge and pay (ATO registered agent lodgment program).
• Lodged on paper, or not eligible for the program: the original date, 28 October 2026, applies. Talk to your agent now.
• Monthly lodgers are on a different cycle: the October 2026 monthly BAS is due 21 November 2026.
• Work in this order: reconcile the bank feed, lift out private use, then check GST codes line by line.
• GST credits follow business use only, and purchases over $82.50 need a tax invoice.

The September quarter dates, checked against the ATO

The ATO publishes these dates on its registered agent lodgment program pages and its business due-date pages. As at November 2026, they read:

Obligation	Due date	When it applies
Quarter 1 (Jul–Sep) 2026-27 BAS, standard date	28 October 2026	The date printed on a quarterly BAS
Quarter 1 BAS you lodge yourself online	11 November 2026	Under the two-week lodgment concession, if you are eligible
Quarter 1 BAS lodged by a registered agent	25 November 2026	Agent lodges electronically, and the previous activity statement was lodged electronically
October 2026 monthly BAS	21 November 2026	Monthly lodgers only
Quarter 2 (Oct–Dec) 2026-27 BAS	28 February 2027	The agent program adds no extra time to quarter 2

A few conditions are worth knowing before you plan your weeks around 25 November:

• Paper lodgment loses the later date. The ATO states that a quarterly activity statement lodged on paper does not receive the lodgment program due dates.
• A GST monthly cycle is excluded from the quarterly program dates, and so are the quarterly instalment notices (Forms R, S and T).
• Clients on a substituted accounting period are only eligible if their quarters line up with the standard quarters.

Your agent can see your actual due date in their own online services, so a one-line email asking "is my September quarter BAS on the 25 November date?" settles it.

Monthly or quarterly: which BAS is yours?

Mixing up the two cycles is the quickest way to lose a week. Per the ATO's BAS due dates page:

• Monthly: required if your GST turnover is $20 million or more, or the ATO has directed you to report monthly. Due on the 21st of the following month.
• Quarterly: the default if your GST turnover is under $20 million. Quarter 1 (July, August, September) is the September quarter.
• Annual GST return: available if you are voluntarily registered and your GST turnover is under $75,000.

Some businesses get both: if you report GST quarterly but have monthly PAYG withholding, you receive a monthly activity statement for the first two months of the quarter and a quarterly one for the third. Check the cycle shown on your statement, or ask your agent, before you treat any date as yours.

Step 1: Reconcile your bank feed to the BAS figures

Start here. A feed that does not tie out tends to surface the other two problems while you work through it, so you meet them in the right order.

1. Total the quarter. Pull every business bank and card transaction from 1 July to 30 September 2026 and compare totals with what feeds the BAS draft: sales, purchases and wages, not one lump sum.
2. Chase the usual gaps. Transfers between your own accounts counted as income or expenses, duplicate imports, loan repayments where only the interest is an expense, and deposits with no invoice behind them.
3. Check timing if you account for GST on a cash basis. Businesses with an aggregated turnover under $10 million can choose cash or non-cash (accruals) accounting for GST. On a cash basis, a sale invoiced in September but paid in October belongs in the December quarter, not this one. On a non-cash basis it belongs here.
4. Agree the closing balance. The balance on 30 September should match your records, so the December quarter starts clean.

If the totals do not tie out, fix the feed before anything goes to your agent. An unexplained difference now is a correction later.

Step 2: Lift private use out of the business figures

Private spending hides in a shared account: groceries on the business card, family fuel, a personal subscription, or a phone and internet bill used for both.

The ATO's rule on when you can claim a GST credit is direct: for a purchase used for both business and private purposes, you claim a credit only for the business part. Record the basis for each split (a vehicle logbook, a usage estimate you can explain) and keep it with the expense.

Illustrative example: a shared phone bill

	Amount
Quarterly phone bill, GST-inclusive	$330.00
GST in the price (one-eleventh at 10%)	$30.00
Business use, from your usage records	60%
GST credit to claim (60% of $30.00)	$18.00
Private share of the GST, not claimable	$12.00

Illustrative figures only, using the 10% GST rate. Anything wholly private moves to drawings, so it stops distorting both your expense totals and your GST credits.

Step 3: Check the GST codes line by line

With private amounts out, the remaining risk is treatment. The amount of GST is rarely the problem; a line under the wrong code is. Work down the quarter and confirm:

• Taxable purchases carry a credit only if the price included GST, you have paid or must pay for them, and they are not for making input-taxed supplies.
• GST-free purchases (basic food, many health and education services) carry no GST and no credit.
• Input-taxed purchases (residential rent, most financial supplies such as bank fees and interest) carry no credit.
• Purchases over $82.50 need a tax invoice from the supplier before you claim the credit. A quick ABN Lookup confirms the supplier is registered for GST.
• Reversals: a refund coded as income, a sale coded as a purchase, or GST claimed on a fee that never included it.

Missed a credit from an earlier quarter? The ATO allows a 4-year time limit for claiming GST credits, so your agent can include it rather than you losing it.

How GST treatment codes feed each BAS label walks through bank fees, interest and equipment examples if a line is unclear.

Illustrative example: the quarter's net GST

BAS figure	Amount
Total sales, GST-inclusive (G1)	$44,000
GST on sales (1A), one-eleventh of taxable sales	$4,000
Business purchases with GST in the price, after private use removed	$13,200
GST credits (1B)	$1,200
Net GST payable for the quarter	$2,800

Illustrative figures, assuming every sale is taxable. Run your own numbers through the free BAS calculator as a sense check before they go to your agent.

The pre-lodgment checklist

Tick these before anything goes to your agent:

1. Your due date confirmed with your agent: 25 November 2026 if the program date applies, or the original date if not.
2. Bank feed totals match the BAS draft for 1 July to 30 September 2026.
3. Closing bank balance at 30 September agrees.
4. Transfers between your own accounts excluded.
5. Private-use transactions removed or split, with the basis recorded.
6. GST codes reviewed line by line, with no credit on private shares.
7. Tax invoices held for purchases over $82.50.
8. Cash or non-cash GST timing applied consistently.

When records were kept through the quarter, this is usually a sitting or two rather than a lost weekend.

What to send your agent, and where 2Fin fits

Your agent lodges the BAS through their own online services; 2Fin keeps the figures underneath it sorted and ready.

2Fin is a tax and money app for employees, sole traders and people who are both. Fin reads your bank feed, sorts each transaction into a category, and applies the GST treatment you set on that category, so each line lands on its BAS label. For Australia, 2Fin prepares the BAS (G1 to G20, 1A and 1B on the accounts method, and W1 and W2) ready for your agent to review and lodge. See GST treatment and BAS labels in 2Fin.

What your agent typically wants, and how it reaches them:

• The BAS figures for the quarter, with the GST treatment behind each label.
• The accountant ledger, journal and profit-and-loss CSVs for the transactions behind them.
• Receipts matched to the larger purchases.
• A standing hand-off, if you prefer: on AUTO+, 2Fin can email activity-statement figures to your account address on a quarterly schedule, and on ELITE+ and AUTO+ you can give a bookkeeper their own sign-in to your books. Automating your bookkeeping handover covers each route.

For a plain-English refresher on what each BAS section reports, read how BAS lodgement works.

Your next step

Today, send your agent one email confirming your September quarter due date, then block out a sitting this week for steps 1 to 3. If you want the December quarter to arrive already sorted, Get 2Fin free and connect your bank feed now, so the October to December figures build up as you go.

General information for Australian businesses, 2026-27, based on ATO guidance as at November 2026. For your own situation, check with your registered tax or BAS agent.