September sits in a strange position on the business calendar. The financial year is three months old, the tax office hasn’t started sending reminders yet, and the Christmas quarter feels far enough away that urgency hasn’t kicked in. That’s exactly why it’s the most valuable month to get your books in order.
By the time October arrives, your Q1 Business Activity Statement is due, Payday Super is in full swing under new rules, and the trading pressure of Q4 starts compressing your time to fix anything that went wrong earlier. The businesses that sail through the Christmas quarter are the ones that used September to check, not scramble.
This checklist covers five specific bookkeeping actions tied to real compliance obligations and financial risks that are live right now. None of them are optional. All of them can be completed before 30 September if you start this week.
What this checklist covers:
- Bank reconciliation ahead of your Q1 BAS lodgement
- Payday Super payment verification under the new 2026 rules
- Debtor ageing review before the Christmas payment crunch
- PAYG withholding reconciliation against your STP data
- Cash flow forecasting for October through December
Check 1: Reconcile Your Bank Accounts Through 30 September
Your Q1 BAS covers the period 1 July to 30 September 2026. The ATO’s due date for self-lodgers is 28 October 2026, with BAS agents getting until 25 November. That sounds like plenty of time but the BAS is only as accurate as the books behind it.
A bank reconciliation that’s three weeks behind when you sit down to lodge means you’re either guessing at your GST figures or spending hours catching up under deadline pressure. Neither is a good option.
What to do before 30 September
- Match every transaction in your accounting software to your bank statement through the end of the month
- Clear any unreconciled items older than 30 days — these are often duplicates, miscoded transactions, or missing receipts that will distort your GST calculation
- Reconcile all business credit cards and merchant accounts, not just the main trading account
- Run a GST audit report in your software to check for transactions coded to the wrong tax treatment
Why this matters beyond compliance
An unreconciled set of books doesn’t just create BAS risk. It means your profit and loss figures are unreliable, your debtor balances may be wrong, and any cash flow forecast you build in Check 5 will be built on shaky ground. Every other check on this list depends on clean data here.
Key action: Set a calendar block for the last week of September to finalise your reconciliation. If you’re more than four weeks behind, start today.
Check 2: Verify Payday Super Is Flowing Correctly
This is the most consequential compliance change of the 2026-27 financial year, and September is when many SMEs are discovering gaps in their setup.
From 1 July 2026, the old quarterly super system is gone. Under Payday Super, employers must now pay super guarantee contributions within 7 business days of each payday. The super guarantee rate is 12% of qualifying earnings. The ATO cross-references your Single Touch Payroll (STP) data against super fund receipts to identify any shortfall, automatically.
The risk is real and immediate. If contributions aren’t received by the fund within 7 business days, the ATO calculates a Super Guarantee Charge (SGC) that includes the unpaid amount, daily interest, and an administrative uplift of up to 60% of the shortfall. Unlike the old system, you no longer self-assess and lodge a statement the ATO issues you a notice of assessment directly.
What to pull and check right now
- Run a super payment report in your payroll software covering July, August, and September to date. Look at the date each contribution was initiated versus the date it was received by the fund.
- Confirm your clearing house setup is working. The Small Business Superannuation Clearing House (SBSCH) closed on 1 July 2026. If you were using it, you need an alternative provider in place now.
- Check your STP reporting includes year-to-date qualifying earnings for each employee, as required from 1 July 2026. This is the data the ATO uses to calculate what you owe.
- Verify the ABN used for super contributions matches the ABN reported in your STP pay events. A mismatch is one of the most common causes of apparent shortfalls under the new system.
The ATO’s first-year approach
The ATO has published PCG 2026/1 setting out a supportive compliance stance for the 2026-27 year. Employers who are genuinely trying to pay on time and fix errors quickly won’t be the primary focus of enforcement action. The focus is on employers who aren’t paying at all, or who are making no effort to comply.
That said, “supportive” does not mean “ignored.” If you’ve had a payment miss or a processing delay, the right move is to pay the shortfall to the fund as soon as possible, before the ATO issues an assessment.
Key action: Pull your super payment report this week. If any payment was received by the fund more than 7 business days after the corresponding payday, address it immediately.
Check 3: Review Your Debtor Ageing Report
Unpaid invoices are a quiet drain that most business owners only notice when cash gets tight. September is the last realistic window to chase overdue accounts before the Christmas quarter compresses everyone’s attention spans and payment cycles.
The pattern is predictable: businesses that don’t chase debtors in September find themselves in November trying to collect on invoices that are now 90-plus days old, from customers who are themselves stretched heading into the holiday period. Collection rates drop sharply the older a debt gets.
How to read your ageing report
Run a debtor ageing report in your accounting software and sort by the oldest outstanding amounts first. The categories to focus on:
| Ageing bucket | Action required |
|---|---|
| 0-30 days | Monitor. Send a statement if not already done. |
| 31-60 days | Send a formal overdue notice. Follow up by phone if there is no response within 5 business days. |
| 60+ days | Call the customer directly this week. Agree on a payment plan or escalate to a debt recovery process. |
| 90+ days | Assess whether the debt is recoverable. Consider a formal letter of demand. |
Anything over 60 days needs a phone call before October. An email is easy to ignore. A direct conversation creates accountability and often surfaces a genuine reason for the delay one that can be resolved before it becomes a write-off.
What to look for beyond the obvious
- Invoices that have been partially paid but not fully cleared. These are easy to miss and often indicate a dispute.
- Customers who appear current because they’ve paid a recent invoice but still owe on an older one.
- Credit notes that haven’t been applied, making a balance appear higher than it is.
Once the Christmas trading period starts, your customers will be harder to reach and slower to pay. Collect in September while conditions are still normal.
Key action: Run your debtor ageing report today. Any balance over 60 days gets a phone call this week, not an email.
Check 4: Reconcile Your PAYG Withholding Against STP
PAYG withholding is one of the most common sources of BAS errors for small employers, and the mismatch usually isn’t discovered until lodgement time when fixing it is more stressful than it needs to be.
The issue is straightforward: the PAYG withholding amount you report on your BAS must match the year-to-date figures your payroll software has reported through Single Touch Payroll. If those two numbers don’t align, you have a discrepancy that the ATO can flag during processing.
How to run the check
- Pull your STP reports for the period 1 July to the most recent pay run. Your payroll software should have a YTD summary report showing total gross wages, PAYG withheld, and super for each employee.
- Compare against your BAS figures. The PAYG withholding amount on your W1 and W2 labels should reconcile directly to your STP data.
- Check for manual adjustments. If any pay runs were processed outside the normal payroll cycle — for example, a termination payment, a bonus, or a correction verify these are captured in STP correctly.
- Confirm all pay events have been accepted by the ATO. Your payroll software should show a status for each STP submission. Any rejected or pending events need to be resolved before you lodge.
Common causes of PAYG discrepancies
- Paying an employee outside the payroll system (cash, direct transfer) without processing a corresponding STP event
- Termination payments coded incorrectly, particularly where different tax treatments apply to different components
- Payroll software updates that changed the withholding calculation mid-period without the operator being aware
The ATO uses STP data as a primary compliance tool, not just for super but for PAYG. Getting your numbers aligned before lodgement is significantly easier than responding to an ATO query after the fact.
Key action: Run a YTD payroll summary from your software and cross-check the PAYG withheld figure against what you plan to report on your Q1 BAS. Any difference needs an explanation before you lodge.
Check 5: Update Your Cash Flow Forecast for October to December
The Christmas quarter is the most financially complex period of the year for most Australian SMEs. Revenue can spike dramatically in retail and hospitality, or dry up completely in professional services and construction. Either way, the cash flow implications need to be mapped out now, while you still have time to act on what you find.
A cash flow forecast built in September gives you six to eight weeks to arrange a credit facility if you need one, negotiate supplier terms if stock purchases are going to peak, or manage your staffing costs before they become a surprise.
What to include in your Q4 forecast
Build your forecast month by month: October, November, December. For each month, map out:
Cash inflows:
- Expected revenue based on trading history and any known seasonal patterns
- Debtor collections (this is where Check 3 feeds directly into this one the faster you collect in September, the better your October opening cash position)
- Any other income: grants, asset sales, loan drawdowns
Cash outflows:
- Wages and payroll costs, including any planned Christmas casual or seasonal staffing
- Super contributions under Payday Super (these are now more frequent, so model them per pay run, not quarterly)
- Stock or inventory purchases, particularly if you need to order ahead for Christmas demand
- Q1 BAS payment due 28 October — this is a significant cash outflow that catches businesses short every year
- Rent, insurance, subscriptions, and fixed overheads
- Any loan repayments or ATO payment plan instalments
The number most businesses miss
The Q1 BAS payment on 28 October is both the largest single compliance payment of the quarter and the one most commonly underestimated. It covers GST collected across the full July-September period. If your trading has been strong in Q1, this figure will be higher than the same period last year. Make sure your forecast accounts for the actual GST liability, not a rough estimate.
Xero’s small business insights consistently show that cash flow management is the leading financial challenge for Australian SMEs. The businesses that forecast proactively are the ones that avoid the reactive scramble of an overdraft call in November.
Key action: Build or update your October-December cash flow forecast before the end of September. Make sure the 28 October BAS payment is explicitly line-itemed, not buried in a general “tax” category.
Bonus Check: Confirm Your Software Is Payday Super Compliant
This one takes ten minutes and could save you a compliance headache in Q2.
Payday Super introduced new STP reporting requirements from 1 July 2026, including the obligation to report year-to-date qualifying earnings for each employee on every pay event. Not all versions of all payroll software were updated to handle this correctly by the time the legislation took effect.
What to verify
- Check that your software version is current. Log in to your payroll platform and confirm you’re running the latest release. If automatic updates are disabled, check the vendor’s release notes for any Payday Super-related updates issued since June 2026.
- Confirm qualifying earnings are being reported in STP. Run a test payroll report and check that the YTD qualifying earnings field is populated for each employee.
- Review your super payment integration. If your payroll software connects directly to a super fund or clearing house to process contributions, verify the integration is active and that payments are being submitted on the correct schedule.
The ATO’s guidance on Payday Super for employers includes a checklist of what software needs to report. If your provider hasn’t issued a Payday Super update, contact them directly before your next pay run.
Key action: Check your software version and run a payroll report to confirm qualifying earnings are being captured in STP. If anything looks wrong, contact your software provider before your next pay run.
Your September Action Summary
Use this table as a quick-reference checklist to track what you’ve completed before the end of the month.
| # | Check | Deadline | Risk if skipped |
|---|---|---|---|
| 1 | Bank reconciliation through 30 September | 30 September | Inaccurate BAS lodgement on 28 October |
| 2 | Payday Super payment report (July-September) | This week | SGC assessment with interest and 60% uplift |
| 3 | Debtor ageing review, calls on 60+ day accounts | This week | Uncollected cash heading into Christmas quarter |
| 4 | PAYG withholding vs STP reconciliation | Before BAS lodgement | ATO discrepancy flag on Q1 BAS |
| 5 | October-December cash flow forecast | 30 September | Underfunded for BAS payment, stock, and staffing |
| Bonus | Software Payday Super compliance check | Before next pay run | Incorrect STP reporting from 1 July 2026 |
The bottom line
September is the quietest compliance month of the financial year. There are no major lodgement deadlines this month, just preparation for the ones that follow. The five checks above are the difference between entering Q4 in control and entering it already behind.
Most of this work takes a few hours, not days. The bank rec, the super report, the ageing review, the PAYG check, and a basic cash flow model can all be done in a single focused session if your books are reasonably current.
If they’re not if you’re behind on reconciliations, unsure about your Payday Super setup, or haven’t looked at your debtor list in months September is the right time to get professional support before the pressure builds.
Balance My Books works with SMEs across Sydney and Australia to keep books current, compliant, and ready for whatever the quarter brings. Whether you need a one-off catch-up or ongoing monthly bookkeeping support, get in touch with the Balance My Books team to discuss what’s right for your business.
