Common BAS Mistakes Businesses Make

A BAS is only as accurate as the bookkeeping behind it. Most BAS errors begin earlier in the process through incorrect coding, missing transactions, incomplete reconciliations, or payroll balances that have not been checked.

Incorrect GST treatment

GST may be claimed where no tax invoice is available, applied to GST-free or input-taxed items, missed on taxable sales, or coded incorrectly on mixed transactions. Loan payments, private expenses, transfers, wages, and super also require the correct treatment rather than a default GST code.

Unreconciled accounts

Bank accounts, credit cards, payment platforms, clearing accounts, and the ATO integrated client account should be reconciled before the BAS is finalised. Unreconciled items can hide duplicate entries, missing receipts, incorrect dates, or transactions posted to the wrong period.

Relying on reports without reviewing the detail

A GST report can total correctly while individual transactions are still wrong. Large, unusual, or inconsistent amounts should be checked. Payroll activity also needs to agree with STP and the relevant balance sheet liabilities before PAYG withholding is reported.

What to do next

Complete reconciliations before preparing the BAS.
Review GST exceptions and large transactions, not only totals.
Use a registered BAS agent when the business needs professional BAS preparation and lodgement support.

Final Thoughts

BAS mistakes are easier to prevent through regular bookkeeping than to fix after several quarters. A structured review process improves both the lodgement and the reliability of the file used for business decisions.

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Chisel Consulting provides structured bookkeeping, BAS, payroll, reporting, and file-review support for businesses across Australia.