Common BAS Mistakes Sydney Businesses Make

A BAS mistake usually starts before the BAS is even opened.

A sale is coded with the wrong GST treatment. A supplier invoice is missing. A transfer between bank accounts is treated as income. Payroll is processed, but PAYG withholding does not match the accounting file. GST collected from customers has already been spent by the time the activity statement is due.

By the time the BAS deadline arrives, the issue feels like a lodgement problem.

Most of the time, it is really a bookkeeping, GST, payroll or cash flow problem that has been building quietly during the period.

I’m Rafal Slowinski, Director of Tax Accounting Group Pty Ltd. When I review BAS for Sydney businesses, I do not treat the activity statement as a simple software report. I look at the transactions behind it, the GST treatment, payroll records, bank reconciliation, cash timing, and any entries that do not align with how the business actually operates.

The  ATO Business Activity Statements guide is a useful starting point because it explains how BAS is used to report and pay taxes such as GST and PAYG. But the real work happens inside the business records before the BAS is lodged.

Mistake 1: Treating GST Collected As Spare Cash

This is one of the most common BAS mistakes I see.

A customer pays an invoice, and the full amount is credited to the bank account. The business uses that money for wages, suppliers, rent, fuel, software, loan payments or owner drawings. Then the BAS period ends, and the GST amount becomes payable.

The BAS feels like a surprise, even though the liability has been building all along.

This is especially common for Sydney businesses with high operating costs. Rent, wages, insurance, subcontractors, stock, transport, tolls, finance payments and supplier bills can quickly consume the bank balance. If GST is not mentally or practically separated from available cash, the BAS payment can feel heavier than expected.

A better habit is to view GST as money passing through the business, not as money the business can freely spend.

That does not mean every business needs a separate GST bank account, but it does mean the owner should know roughly how much GST is building during the period. If the BAS amount is always causing stress, the issue may not be just the BAS. It may be cash flow planning.

If BAS is already putting pressure on your business, my page on  BAS accountant in Sydney explains how I review the figures behind the activity statement before lodgement.

Mistake 2: Trusting The Software Without Checking The Coding

Accounting software can help, but it does not remove the need for review.

A bank feed can import transactions. A dashboard can show numbers. A GST report can be generated. But the software still depends on how transactions have been entered, matched, and coded.

If the coding is wrong, the BAS can be wrong.

A transfer between accounts may be coded as income. A loan repayment may be coded as a normal expense. A private cost may be treated as fully business-related. A supplier bill may be entered with GST when there was no GST on the invoice. A sale may be coded as GST-free when GST should have applied.

The software can make the file appear active even when the numbers are still unreliable.

When I review a BAS, I look beyond the report. I want to know whether the transactions feeding that report make sense. That may include reviewing sales, expenses, GST codes, bank reconciliation, payroll entries, supplier bills, customer invoices and unusual transactions during the period.

If Xero is part of the problem, my page on  Xero help in Sydney explains how I review the accounting file behind the dashboard.

Mistake 3: Claiming GST Credits Without The Right Records

GST credits are not something to guess.

The ATO explains that businesses can generally claim GST credits for GST included in the price of goods bought for business use, but the rules and records must support the claim. You can read the ATO’s guidance here:  When you can claim a GST credit.

The problem is that a bank transaction does not always prove GST.

A payment to a supplier might include GST. It might not. It might be GST-free. It might be partly private. It might relate to a loan, transfer, tax payment or asset purchase that needs different treatment.

For BAS purposes, I usually want to see the tax invoice or supporting document before relying on the GST credit.

Common problems include:

• missing supplier invoices
• receipts that do not show GST clearly
• expenses coded with GST when the supplier did not charge GST
• private-use expenses claimed fully
• bank transactions used as evidence without checking the invoice
• subscriptions or overseas software costs treated incorrectly
• asset purchases entered as ordinary expenses without review

GST credits can reduce the BAS amount payable, but they need to be supported. If the records are weak, the BAS position is weak.

The ATO’s  GST records guidance explains that businesses need records showing the income and expenses used to calculate and support GST credits.

Mistake 4: Forgetting That PAYG Withholding May Also Sit In The BAS

Some business owners think BAS is only about GST.

For employers, BAS may also include PAYG withholding.

If you withhold tax from employee wages, those amounts generally need to be reported and paid through the activity statement. The ATO’s page on  PAYG withholding explains that withheld amounts are reported in the PAYG tax withheld section of the BAS.

This is where payroll and BAS connect.

If payroll reports do not match the accounting file, the BAS figure may not be reliable. If wages have been coded incorrectly, pay runs have not been matched properly, or PAYG withholding has not been tracked clearly, the activity statement can carry the error forward.

For Sydney businesses with staff, I usually check whether:

• payroll reports match the accounting file
• PAYG withholding has been recorded properly
• wages and super are separated clearly
• pay runs are matched to bank payments
• employee records are up to date
• payroll liabilities make sense on the balance sheet

If payroll is not clean, BAS review becomes harder.

If this is where your business is struggling, my page on  payroll services in Sydney explains how I integrate payroll records with bookkeeping, BAS, and tax work.

Mistake 5: Lodging Before The Bank Accounts Are Reconciled

A BAS should not be lodged from unreconciled records.

If the bank accounts have not been reconciled, the accounting file may not reflect what actually happened during the period. Transactions may be missing, duplicated, unmatched or sitting in suspense. Customer payments may not be matched to invoices. Supplier payments may not be matched to bills. Transfers may be sitting in the wrong place.

The BAS report may still produce a number.

That does not mean the number is ready.

Bank reconciliation is one of the simplest checks, but it is also one of the most important. If the business bank account, credit card, loan account, or payment platform does not align with the accounting file, the GST and PAYG figures may be based on incomplete information.

Before lodging, I want to confirm that the main accounts have been reconciled and that any obvious unknown items have been reviewed.

If the bookkeeping is behind, my page on  small-business bookkeeping in Sydney may be a better starting point before the next BAS is prepared.

Mistake 6: Coding Transfers As Sales

This mistake can distort both BAS and financial reports.

A business owner transfers money between accounts, moves funds from a loan account, receives money from the owner, transfers savings into the business or moves money between business accounts. The bank feed imports the transaction, and it gets coded as income.

That can make sales look higher than they really are.

It can also create a GST problem if the transfer is treated as a taxable sale.

A bank deposit is not always business income. It might be a transfer, loan, owner contribution, reimbursement, refund, capital injection or movement between accounts.

When I see an unusual deposit in a BAS period, I want to know what it actually represents before accepting the coding. This is especially important for businesses with multiple bank accounts, merchant facilities, loan redraws, director contributions or transfers between personal and business accounts.

A BAS should report business activity, not mislabelled money movement.

Mistake 7: Treating Loan Repayments As Normal Expenses

Loan repayments can confuse BAS and profit reports.

A repayment may include interest, principal and fees. The interest may be deductible in some circumstances, but the principal repayment is not usually treated the same way as an ordinary business expense. If the whole repayment is coded to an expense account, the profit and loss report may be distorted.

GST treatment can also become messy if loan payments are coded without review.

This can happen with vehicle finance, equipment finance, business loans, credit cards, overdrafts or director-related lending.

For BAS purposes, I want to understand what the payment relates to and whether the accounting file properly separates interest, principal, fees, and any other components.

A loan payment is not the same thing as buying materials or paying rent. If it is coded casually, the BAS and tax records can both become harder to explain.

Mistake 8: Missing Supplier Bills Before Claiming GST Credits

Some businesses prepare BAS based solely on payments.

Others use supplier bills entered into the accounting system. Either way, missing bills can create problems.

If supplier bills are not entered, the business may miss GST credits or misread its GST liability. If bills are entered twice, GST credits may be overstated. If bills are entered but payments are not matched properly, accounts payable reports may become unreliable.

This is particularly common in businesses with many suppliers, subcontractors, stock purchases, materials, food suppliers, software subscriptions or recurring bills.

For Sydney cafes, trades, online stores and service businesses, supplier records can quickly spread across emails, statements, apps and paper receipts.

I usually want to check:

• Are supplier bills entered for the right period?
• Are tax invoices available?
• Have payments been matched?
• Are duplicate bills present?
• Are personal or mixed-use costs separated?
• Are GST codes correct?
• Do supplier statements agree with the file?

A BAS prepared from incomplete supplier records can be wrong even if the software report looks clean.

Mistake 9: Handling Deposits And Progress Payments Incorrectly

Deposits and progress payments can create BAS confusion.

A builder, tradie, consultant, event business, creative agency, online store or service provider may receive money before the work is complete. The payment may be a deposit, part payment, progress claim, prepayment or final payment.

The accounting treatment depends on the facts.

If the payment is simply coded without thought, the BAS can report GST in the wrong period, or the income can be misunderstood. The invoice wording, contract terms, accounting basis and GST rules can all matter.

This is why I prefer to review the actual transaction rather than rely on a generic label.

• What was invoiced?
• When was it paid?
• Was GST included?
• Was it a deposit or payment for work already performed?
• Has the final invoice been issued?
• Does the accounting file match the customer record?

Deposits and progress payments are common in Sydney trade businesses, professional services, events, construction-related work and project-based businesses. They should not be guessed at the end of the BAS period.

Mistake 10: Not Reviewing Private Use Or Mixed-Use Expenses

Some expenses are partly business and partly private.

Phone, internet, vehicles, home office costs, travel, meals, subscriptions and some equipment purchases can all include a private element depending on how they are used.

If a mixed-use expense is treated as fully business-related, both the BAS and the tax return may be affected.

This can also affect GST credits. A business may need to claim only the business portion of GST rather than the full amount.

For example, a phone used for both business and family calls needs a reasonable business-use basis. A vehicle used for job sites and personal driving needs to be recorded. A home internet service used by the household and the business should not be treated as entirely business without review.

The claim needs to match the use.

A clean BAS review should identify expenses where private use may need to be separated before the activity statement is lodged.

Mistake 11: Ignoring Unusual Transactions

Every BAS period usually has a few ordinary entries and a few unusual ones.

The unusual entries are where mistakes often sit:

• A vehicle purchase.
• A large refund.
• An insurance payout.
• A loan drawdown.
• A related-party payment.
• A director paying a business bill personally.
• A business sale or asset sale.
• A property-related transaction.
• A large software or equipment purchase.
• A supplier credit.
• An overseas payment.
• An ATO payment or refund.

These transactions should not be treated like normal weekly expenses.

They may affect GST, BAS, tax deductions, depreciation, loans, director accounts, capital gains tax or other areas of the file.

When I review BAS, I look for entries that do not fit the normal pattern. Those entries deserve a pause before lodgement because the wrong treatment can carry over into the BAS, financial reports, and tax return.

If the transaction involves GST uncertainty, my  GST advisor page in Sydney explains how I review the tax treatment behind the invoice, contract, or BAS figure.

Mistake 12: Leaving BAS Review Until The Due Date

A BAS problem becomes harder when the deadline approaches.

The business owner is under pressure. The bookkeeper is chasing missing invoices. Payroll reports need checking. The accountant is trying to review figures quickly. The owner wants the BAS lodged, but the records are not ready.

That is when guesses happen.

A better approach is to review the file before the due date becomes urgent.

That may mean checking the bookkeeping monthly, reviewing GST coding during the period, keeping supplier invoices current, matching customer payments, reconciling bank accounts, and monitoring the likely BAS amount as the quarter progresses.

BAS should not be a surprise event. It should be a reporting point based on records kept in reasonable order during the period.

Mistake 13: Not Understanding Why The BAS Amount Changed

A BAS figure can change for good reasons.

Sales may have increased. GST credits may be lower. Payroll may have increased PAYG withholding. A large asset purchase may have changed GST credits. A prior-period correction may have flowed through. A customer deposit may have been received. A business may have moved from smaller jobs to larger invoices.

The mistake is not always the number.

The mistake is lodging without understanding what drove it.

When a BAS is higher or lower than expected, I want to compare the BAS to the business activity. If the figure makes sense, the business owner should understand why. If it does not make sense, we need to find the coding, reconciliation, payroll or GST issue before lodging.

A BAS review should leave the owner clearer, not simply relieved that the form was submitted.

Mistake 14: Forgetting That BAS Affects The Tax Return Later

BAS is not separate from the annual tax return.

GST, PAYG withholding, payroll, sales, expenses, asset purchases and bookkeeping records during the year all feed into the year-end position. If each BAS is prepared from weak records, the tax return may inherit those weaknesses.

That can create extra work later.

BAS figures may not reconcile to annual accounts. GST may need review. Payroll may not match. Supplier bills may be missing. Income may be overstated or understated. The profit and loss report may not reflect the real business.

A BAS should help keep the year organised.

If each BAS period is reviewed properly, tax return preparation becomes easier, and the business owner has a better view of the year before it closes.

What I Look At Before Lodging BAS For A Sydney Business

When I review a BAS, I usually want to see the records behind the activity statement, not only the final number.

Depending on the business, that may include:

• sales invoices
• supplier bills
• GST reports
• PAYG withholding reports
• payroll summaries
• bank reconciliation
• accounts receivable
• accounts payable
• credit card transactions
• loan payments
• asset purchases
• private-use adjustments
• unusual deposits
• ATO payment history
• software reports from Xero, MYOB or QuickBooks

I also want to understand the business context. A BAS for a cafe is different from a BAS for a tradie, an online store, a consultant, a medical practice, a startup, or a company with payroll.

The activity statement should reflect the actual business activity for the period.

A Better BAS Habit For Sydney Businesses

The best BAS process is not complicated.

It is consistent.

• Keep invoices as they arrive.
• Code transactions during the period, not after the deadline.
• Review GST treatment before lodging.
• Reconcile bank accounts.
• Check payroll reports.
• Match payments to invoices and bills.
• Watch the GST collected during the quarter.
• Review unusual transactions early.
• Ask questions before guessing.
• Understand the BAS amount before paying it.

Those habits make BAS less stressful and tax time more reliable.

They also provide the business owner with better information throughout the year. If BAS is always a scramble, the business is probably not getting useful financial information between lodgements.