A BAS can look ready because every bank transaction has been reconciled and the software produces a neat report. That is a good start. It is not proof that every tax code, timing decision and credit is correct.
The best review gives extra attention to transactions that are unusual, large or easy to misclassify. You do not need to turn each quarter into an archaeological dig. You need a repeatable process that makes the exceptions visible.
Begin with the period and the accounting method
Confirm which BAS you are preparing and which obligations appear on it. GST, PAYG withholding and PAYG instalments are different items. A movement in one does not automatically explain a movement in another.
Then check whether GST is reported on a cash or non-cash basis. The timing can differ between money being received or paid and invoices being issued or received. Running a report on the wrong basis can produce plausible numbers for the wrong period. The ATO outlines the methods in its GST accounting guidance.
Reconcile bank and credit card accounts, but also review clearing accounts, unpaid invoices and supplier bills. Match loan balances and payment allocations where finance is involved. The software can only report the information and classifications it has been given.
Some payments deserve a deliberate pause
Review insurance, overseas subscriptions, government charges, motor vehicles, asset purchases, reimbursements and private spending. A supplier name is not enough to decide the GST treatment. One supplier can issue invoices containing several different kinds of charge.
Wages, loan principal and owner transfers should not acquire GST merely because a rule automatically categorised the bank payment. Equally, matching a payment against an existing bill should not create a second expense and a second credit.
Illustrative example: A business receives a $1,100 invoice for a taxable purchase and enters it as a bill. When the payment arrives in the bank feed, it is accidentally coded as a new expense instead of matched to the bill. The books now contain two expenses for one purchase. Depending on reporting settings and timing, the error can also distort GST. A review of duplicate amounts and unpaid bills helps expose the mismatch.
A bank statement does not replace every tax invoice
As checked on 8 September 2026, you generally need a tax invoice to claim a GST credit for a purchase costing more than $82.50 including GST. Other conditions also apply, including the business purpose and the GST treatment of the supply. The ATO’s credit requirements explain what to check.
Attach the invoice to the transaction while it is easy to find. If a supplier charged no GST, do not manufacture a credit by dividing the payment by eleven. For purchases used partly privately, identify and support the business portion. The ATO separately explains situations where a credit cannot be claimed.
These checks also make future conversations easier. “Invoice missing, requested from supplier on Tuesday” is an actionable note. An empty attachment field and a guessed tax code leave the next person starting from scratch.
Compare the quarter with the story of the business
Look at sales and GST against previous periods. Has a major contract ended? Was equipment purchased? Did customer payment timing change? A large movement may be entirely correct, but it should have an explanation.
Review the balance sheet as well as the BAS report. A growing suspense account, unexplained tax balance or stale creditor can reveal a problem that a sales comparison misses. Keep a short reconciliation showing how the BAS relates to the accounting records.
If you find an older mistake, correct it properly
Do not quietly push every historical error into the next quarter. Whether a GST error can be corrected in a later BAS depends on its type and the applicable conditions, including time and value limits. Some errors require revision of the original BAS. The ATO’s correction guidance sets out the framework.
Write down the affected transaction, original period, reason for the error and proposed correction. Keep the explanation with the BAS working papers. That creates a clear trail and reduces the chance of correcting the same item twice.
Before approving lodgment, ask for the final amount payable or refundable and the due date. Arrange the payment and save the lodgment confirmation. The ATO’s BAS tips provide another useful reference. A reliable BAS process should leave you with an understandable number and a cleaner set of books for the next decision.
Target Advisory 