7 Common BAS Mistakes Mornington Peninsula Business Owners Make (and How to Fix Them)

If you run a business on the Mornington Peninsula — whether that's a Mornington café, a Rosebud trade business, or a Mount Eliza allied health clinic — Business Activity Statements are one of those recurring compliance jobs that's easy to get wrong when you're flat out. We review BAS lodgements for local businesses every quarter, and the same handful of mistakes come up again and again. Here's what they are, why they matter, and how to fix them for good.

1. Missing lodgement dates and due dates

Quarterly BAS is generally due on the 28th of the month following the quarter (28 October, 28 February, 28 April, 28 July), with a slightly later date for the December quarter. Miss it, and the ATO can apply a Failure to Lodge (FTL) penalty in 28-day increments, plus General Interest Charge (GIC) on any amount owing.

• The fix: Set calendar reminders two weeks out from each due date, not on the day itself.
• Lodging through a Registered BAS Agent often extends your due date by around four weeks — a genuine buffer for seasonal peninsula businesses juggling summer trade.
• If you're going to be late regardless, contact the ATO or your BAS agent before the due date — proactive communication can reduce penalties.

2. Coding transactions with the wrong GST treatment

Not everything attracts 10% GST. Basic food, most health services, and certain financial supplies are GST-free or input-taxed under the A New Tax System (Goods and Services Tax) Act 1999. We regularly find local businesses coding bank fees, interest, or residential rent as "GST on Expenses" in Xero, which overstates their GST credits.

• The fix: Set up Xero bank rules correctly from the start, mapped to accurate tax rates (GST Free, BAS Excluded, Input Taxed).
• Review your chart of accounts default GST settings annually — supplier terms and product lines change.
• Run a GST Reconciliation report in Xero before every lodgement to catch anomalies.

3. Claiming GST credits without a valid tax invoice

Under GST law, you can only claim an input tax credit if you hold a valid tax invoice for purchases over $82.50 (GST-inclusive). We often see businesses claim GST off a bank statement line alone, with no invoice on file — a common trigger for ATO review and repayment demands.

4. Getting PAYG withholding wrong

If you employ staff — think seasonal hospitality workers in Rye or trade apprentices in Hastings — you must withhold PAYG tax from wages and report it correctly on your BAS (or IAS). Common errors include using outdated tax tables, missing STP (Single Touch Payroll) reconciliation against BAS figures, or forgetting to withhold from contractors who've provided an invalid ABN.

• The fix: Run payroll through Xero with STP Phase 2 enabled so PAYG figures flow automatically and match your BAS.
• Reconcile your payroll activity statement against BAS labels W1 and W2 every lodgement.
• Check contractor ABNs at abr.business.gov.au before paying — no valid ABN generally means you must withhold at the top marginal rate.

5. Lodging before the bank accounts are reconciled

This is the single biggest driver of BAS amendments we see. Business owners run BAS reports in Xero straight from unreconciled bank feeds — meaning duplicate transactions, uncoded transfers, and missing invoices all flow straight into GST figures.

• The fix: Reconcile every bank and credit card account to zero before pulling your BAS report.
• Use Xero's Bank Reconciliation Summary report to confirm your reconciled balance matches your bank statement close.
• Review the GST Detail report line by line for anything sitting in a suspense or uncategorised account.

6. Mixing personal and business transactions

Sole traders and small partnerships across the Peninsula often run one account for everything. This makes it near-impossible to separate deductible business expenses from private spending, and it slows down every single BAS cycle because someone has to manually sift through the noise.

• The fix: Open a dedicated business transaction account and card, even as a sole trader.
• Feed that account directly into Xero and apply bank rules so recurring business expenses code themselves.
• Any genuinely mixed-use purchases should be split and apportioned at the time of coding, not guessed at quarter-end.

7. DIY lodgement without a Registered BAS Agent

Under the Tax Agent Services Act 2009 (TASA), only a Registered BAS Agent or Tax Agent can legally prepare and lodge a BAS on your behalf for a fee. Some business owners lodge themselves without properly understanding GST classification rules, then discover errors months later when the ATO flags a discrepancy.

• The fix: Engage a Registered BAS Agent (check the register at tpb.gov.au) who reviews and lodges on your behalf, with professional indemnity insurance behind the work.
• A good BAS Agent doesn't just lodge — they flag issues in your bookkeeping before they become ATO problems.
• You retain legal responsibility for the accuracy of your BAS regardless of who lodges it, so choose someone who checks the detail, not just the deadline.

The pattern behind all seven mistakes is the same: BAS goes wrong when the bookkeeping behind it isn't tidy, timely, and reviewed by someone who understands GST law. If any of these sound familiar, start by reconciling your last quarter properly, checking your Xero GST codes against actual invoices, and getting a Registered BAS Agent to run an eye over your next lodgement before it goes in. It's a lot cheaper than an ATO amendment.