Finding a possible BAS mistake does not automatically mean you should amend the return or lodge a replacement. First establish whether you have an error, a later adjustment, or records that are incomplete or inconsistent.
That distinction affects the evidence you need and the next action. This guide explains how to check BAS errors in Parramatta, what to review before lodging, what to preserve after lodgement, and how to assess local BAS support.
Quick summary
- Compare the BAS with bank records, invoices, payroll reports and other source documents before changing figures.
- An error existed when the BAS was lodged. An adjustment results from a later event affecting an amount that was correct at lodgement.
- Review GST treatment, reporting periods, duplicated or missing transactions and PAYG-related figures.
- Keep the lodged BAS and supporting records if you find a problem after lodgement.
- When choosing help, confirm the review scope, correction responsibilities and whether the provider is registered where registration is required.
Is It a BAS Error, an Adjustment, or a Records Issue?
The Australian Taxation Office distinguishes an error or mistake from an adjustment. An error means an amount was incorrect when the BAS was lodged. An adjustment applies when the amount was correct at lodgement, but a later sale, purchase or other event changed it. See the ATO explanation of BAS errors and adjustments for the formal distinction.
| Situation | What it means | First question to ask |
|---|---|---|
| Error | The BAS contained an incorrect amount when lodged. | Which source record or calculation was wrong? |
| Adjustment | The original amount was correct, but a later event changed the position. | What happened after lodgement? |
| Records issue | The available information does not support a reliable conclusion. | Which document, reconciliation or report is missing? |
Do not classify an issue solely because a current accounting report differs from an earlier BAS. Identify the reporting period, underlying transaction and timing of the change. If the records do not answer those questions, treat the matter as unresolved rather than guessing.
What to Check Before Lodging a BAS
A BAS review should begin with source records, not just final totals. The ATO’s BAS guidance covers reporting and paying GST and PAYG amounts, but the supporting records still need to be accurate and complete.
Confirm the reporting period
Check that sales, purchases, payments and payroll information belong in the period being reported. A transaction recorded in the wrong month or quarter can make the BAS appear incorrect even when the underlying amount is valid.
Reconcile the bank accounts
Unreconciled transactions can leave sales, expenses, transfers or fees missing, duplicated or incorrectly dated. Compare the accounting records with bank statements and investigate unmatched items instead of carrying them forward without explanation.
Regular bookkeeping support can help keep records current through bank reconciliations, coding and regular reports before BAS preparation. It does not replace a decision about the correct GST or PAYG treatment, but it can make discrepancies easier to identify.
Review sales and purchases
Check invoices, credit notes, receipts and other source documents against sales and purchase totals. Look for missing documents, duplicate entries, transactions posted to the wrong account and credit notes that have not been reflected correctly.
Inspect GST treatment
Review whether each relevant transaction has the appropriate GST treatment for its circumstances. Pay particular attention to unusual purchases, mixed business and private use, GST-free or input-taxed items, and transactions where the tax invoice or supporting evidence is incomplete.
Check payroll-related figures
Where PAYG withholding or other payroll-related amounts are reported, compare the BAS figures with payroll reports and payment records for the same period. Differences may result from timing, incomplete payroll records or an incorrect figure being transferred into the BAS workflow.
Common BAS Mistakes Worth Investigating
These are risk areas to investigate, not proof that a particular Parramatta business has made an error. Match each concern to evidence.
- Unreconciled bank transactions: Compare unmatched deposits and payments with invoices, receipts and transfers. Confirm that owner transactions have not been treated as ordinary sales or expenses.
- Incorrect GST coding: Review the tax code applied to unusual, private-use, GST-free or input-taxed transactions.
- Missing or duplicated invoices: Match transaction listings to the underlying documents. A duplicate purchase can inflate credits, while a missing sale can understate reported amounts.
- Sales recorded in the wrong period: Compare invoice dates, payment records and the business’s reporting basis.
- Incomplete supporting documents: Mark transactions where the records do not explain the amount, GST treatment or business purpose.
- Incorrect PAYG figures: Compare the BAS amount with payroll summaries and payment records rather than copying a figure from a previous period.
A single unusual transaction may not change the treatment of the whole BAS. Repeated unexplained differences, however, suggest that the records or process need a broader review.
A Pre-Lodgement Checklist for Parramatta Businesses
Use this checklist to locate discrepancies before lodging. It helps identify questions, but it cannot determine the correct treatment in every situation.
- Confirm the business name, reporting period and accounting method used.
- Reconcile each relevant bank account and investigate unmatched transactions.
- Compare sales totals with invoices, receipts, deposits and credit notes.
- Compare purchases with supplier invoices and check for duplicates or missing documents.
- Review GST codes on unusual, private-use, GST-free or input-taxed transactions.
- Match payroll and PAYG information to payroll reports and payment records.
- Check prior-period amounts carried forward and explain any movement.
- Save reports, invoices, reconciliations and calculations supporting the figures.
- List unresolved items separately instead of forcing them into a category without evidence.
If the checklist exposes a difference, pause and document what you found. Note the affected transaction, period, BAS label or report, and the evidence still required. That makes any later review more focused.
What to Do If You Find a Mistake After Lodgement
Preserve the lodged BAS and the source records used to prepare it. Identify the affected period and figures, then determine whether the amount was wrong at lodgement or whether a later event changed an amount that was correct at the time.
Do not assume every problem should be handled by changing the next BAS or repeating the original lodgement. The appropriate correction depends on the facts, issue type and applicable ATO process. Review current ATO guidance or obtain qualified advice before making a correction, particularly where GST, PAYG or several reporting periods are involved.
Keep a written explanation of the issue, records reviewed and conclusion reached. If you cannot establish what happened, describe it as an unresolved records issue and seek help with the investigation rather than selecting a correction method based on an estimate.
How to Choose BAS Help in Parramatta
Before engaging a provider, ask exactly what will be reviewed and who will be responsible for identifying and correcting records issues.
- What is included? Ask whether the work covers BAS preparation, a historical correction, bookkeeping, reconciliations, GST coding, payroll information or only a final review.
- Which records are needed? Clarify whether the provider needs bank statements, invoices, accounting-file access, payroll reports and prior BAS documents.
- Who handles uncertainty? Ask how missing documents, mixed-use expenses and differences between reports will be escalated.
- Who is responsible for corrections? Confirm whether the provider will explain the issue, prepare corrected figures or lodge the relevant material.
- Is the provider appropriately registered? The Tax Practitioners Board states that anyone providing BAS services for a fee or reward generally must be registered unless an exemption applies. Check the provider’s position rather than assuming every bookkeeping service can provide BAS advice.
- How will documents be exchanged? Agree how records, approvals and explanations will be shared if you work online.
The Tax Practitioners Board’s information about registered BAS agents highlights the risks of using unregistered preparers, including incorrect or incomplete submissions and possible consequences for the client.
Businesses dealing with repeated mistakes may benefit from broader BAS support. Bookkeeping clean-up may be the right starting point when records are incomplete, while a BAS review or tax advice may be more appropriate when the figures are supported but the treatment is uncertain.
Where Local BAS Support May Fit
Advanced Accounting Taxation & Business Services offers accounting, tax, BAS, bookkeeping and advisory support from Parramatta, Liverpool and online. Its bookkeeping service covers bank reconciliations, coding and regular reports, which may suit a business that needs records brought up to date before a BAS review.
The firm also provides support through its Parramatta and Liverpool offices, with Australia-wide virtual assistance and options to meet online or face to face. This gives business owners a choice between local meetings and a remote document-based process.
Next Steps After Finding a BAS Problem
- Before lodgement: Correct the underlying records, rerun relevant reports and review the BAS totals again.
- After lodgement with a clear discrepancy: Preserve the lodged information, identify the affected period and seek advice on the applicable correction process.
- With incomplete or conflicting records: Arrange a structured records review before deciding whether the issue is an error or an adjustment.
If you need a Parramatta, Liverpool or online discussion about BAS preparation, bookkeeping or a suspected BAS issue, contact Advanced Accounting Taxation & Business Services and explain which period and records require attention.
Frequently Asked Questions
What is the difference between a BAS error and a BAS adjustment?
An error means the amount was incorrect when the BAS was lodged. An adjustment applies when the amount was correct at lodgement but a later event changed it. Establishing when the problem arose is the first step.
Should I lodge a BAS if I have found a possible mistake?
Do not decide based only on a difference in an accounting report. Identify the discrepancy, confirm the reporting period and check current ATO guidance or qualified advice if the figures cannot be verified.
What records should I gather before asking someone to review a BAS error?
Gather the lodged or draft BAS, bank statements and reconciliations, sales and purchase invoices, credit notes, accounting reports, payroll records, PAYG information and notes explaining unusual transactions.
Do I need a registered BAS agent to prepare or correct a BAS?
Anyone providing BAS services for a fee or reward generally must be registered with the Tax Practitioners Board unless an exemption applies. Confirm the provider’s registration status and exact service before engaging them.
Can a Parramatta accountant review BAS records online?
Yes, when the provider offers virtual support and you can securely provide the required records. Ask how documents, approvals and follow-up questions will be handled before work begins.
Make the Next BAS Decision From the Records
The safest response to a suspected BAS mistake is not to guess whether it is an error, adjustment or bookkeeping problem. Trace the figure to its source, establish when the issue arose, preserve the evidence and choose the review or correction path that fits the facts.
For businesses in Parramatta, local or online assistance can help when reconciliations, GST treatment, PAYG figures or prior-period records do not line up. Contact Advanced Accounting Taxation & Business Services for BAS, accounting and bookkeeping support from Parramatta, Liverpool or online.