The first quarter of the 2026–27 financial year closed on 30 September, which puts the Q1 BAS squarely in front of you. The standard due date is 28 October 2026.
Most of the pain around BAS isn't the lodgement itself. It's discovering, the night before, that three months of bank feeds haven't been reconciled. This is the checklist we work through with clients, in the order that saves the most time.
You may have longer than 28 October. Two concessions apply to Q1, and plenty of businesses never use them. Details below.
First: confirm your actual due date
The 28 October date applies if you lodge on paper. Lodge online yourself and you generally get an extra two weeks. Lodge through a registered tax or BAS agent and the concession is longer again.
| How you lodge | Due date |
|---|---|
| Paper | 28 October 2026 |
| Online, self-lodged | 11 November 2026 |
| Through a registered agent | Typically 25 November 2026 |
The online concession applies automatically, with no application needed. Having an accountant isn't enough on its own for the agent date — the BAS needs to be lodged through the agent, and you need to be on their lodgement list before the original due date.
The pre-lodgement checklist
Work through these in order. Each step depends on the one before, so skipping ahead usually means doing it twice.
1. Reconcile the bank
- All three months of bank feeds imported and matched
- Closing balance agrees to the bank statement at 30 September
- Credit cards and loan accounts reconciled
- Unreconciled or suspense items investigated and cleared
If your books are well behind, our bookkeeping clean-up and catch-up service can get them ready before your due date.
2. Check sales and income
- All invoices for the quarter raised and entered
- Sales total agrees to your accounting records, not just the bank
- GST-free and input-taxed sales coded correctly
3. Review purchases and GST credits
- Supplier bills entered for the full quarter
- Tax invoices held where GST is being claimed
- GST coding reviewed, especially the traps below
- Private-use portions apportioned rather than claimed in full
4. Payroll and PAYG withholding
- Payroll finalised and reported through STP
- PAYG withholding agrees to your payroll reports
- Super paid within 7 business days of each payday
5. Final review
- PAYG instalment checked, and varied if circumstances have changed
- Compared with last quarter — anything unexpectedly different?
- Payment arranged for the same date as lodgement
Super works differently this year
Payday Super started on 1 July 2026, so there's no quarterly super deadline alongside your BAS any more. Contributions must reach your employees' funds within 7 business days of each payday. See our Payday Super update, or our payroll and STP services if you would like help keeping up.
Want this checklist in a workbook?
Our toolkits pull your quarterly GST figures together automatically and include a quarterly review checklist.
View the Toolkits →GST coding traps we see most often
- Bank fees and interest — generally input-taxed or GST-free
- Government fees and charges — many council rates, ASIC fees and licences carry no GST
- Insurance premiums — stamp duty within the premium isn't subject to GST
- Overseas software subscriptions — treatment depends on how the supplier is registered
- Motor vehicle running costs — apply the business-use percentage, not the full amount
- Entertainment — GST credits are limited where the expense isn't deductible
If the cash isn't there
Lodging and paying are separate obligations. Lodging on time but paying late attracts interest; not lodging can attract a failure-to-lodge penalty as well, even where the BAS shows nil or a refund. If funds are tight, lodge anyway and talk to the ATO or your adviser about a payment arrangement.
ATO interest is no longer tax deductible. General interest charge on unpaid ATO amounts stopped being deductible from 1 July 2025, so it's now a straight cost to your business.
Other October dates
| Date | What's due |
|---|---|
| 21 October 2026 | September monthly BAS |
| 28 October 2026 | Q1 BAS if lodging on paper; Q1 PAYG instalment |
| 31 October 2026 | Self-lodged tax returns; last day to join a tax agent's client list |
General information only. This article doesn't take into account your circumstances and isn't personal tax, accounting, legal or financial advice. Confirm your position with the ATO or your registered adviser before acting.