How to tackle a higher‑than‑expected BAS
Start with the components that drive your BAS: GST on sales and purchases, PAYG withholding from payroll, and PAYG income tax instalments. Compare this period to the last period and to the same period last year to isolate the change.
- GST: A surge in taxable sales or fewer claimable purchases will increase net GST payable.
- PAYG withholding: Hiring, back pay or bonuses push this up immediately.
- PAYG instalments: The ATO can uplift instalments after your latest return. You can request a variation if it doesn’t reflect current year profit.
Australian context to keep in view
- The BAS reports GST, PAYG withholding, and (for many businesses) PAYG income tax instalments to the ATO on a monthly or quarterly cycle.
- You can report on a cash or accrual basis. On cash, GST is reported when money is received/paid. On accrual, it’s when invoices are issued/received.
- Lodging through a registered BAS agent or tax accountant can provide extended due dates and a formal review process.
- If you have PAYG withholding but are not registered for GST, you may lodge an IAS rather than a BAS; similar checks apply.
What typically makes BAS totals jump
- Large one‑off invoices or milestone billings with GST this period.
- Delayed supplier bills or fewer purchases, reducing input tax credits.
- Cash/accrual mismatch or a basis change mid‑year.
- Adjustments or corrections from prior periods flowing into this BAS.
- New staff, higher payroll, or bonus runs increasing PAYG withholding.
- An ATO uplift in PAYG instalments after your last tax return.
- GST coding errors (e.g., applying 10% GST to wages, loan repayments, or GST‑free items like fresh food, exports, medical, education).
- Asset purchases or disposals, private use adjustments, or entertainment expenses with limited credits.
Diagnose it quickly in your software
Step 1: Reconcile the big movements
Run GST summary/detail reports for the BAS period and compare to the prior period. Sort by tax rate and by largest transactions. Look for unusual GST codes on big invoices or bills.
Step 2: Check your BAS basis
Confirm whether you lodge on cash or accrual. If your debtors jumped, accrual BAS will rise even if cash hasn’t been received. On cash, late‑paid invoices may defer GST into the next period.
Step 3: Review payroll
Run a PAYG withholding report for the period. Compare headcount, gross wages and any bonus/termination runs to explain the change.
Step 4: Inspect PAYG instalments
Check the instalment amount/rate showing on the BAS. If it doesn’t reflect current trading, consider a variation. Get advice before varying to avoid underpayment interest.
In Xero, MYOB and QuickBooks Online you can drill from the GST/BAS report to the underlying transactions and fix incorrect tax codes before you finalise the BAS. If you’re unsure, a bookkeeper or BAS agent can reconcile it with you.
Cash vs accrual for BAS: why it matters
- Accrual basis: GST is reported when invoices are issued/received. Big debtors or unbilled costs can distort the period result.
- Cash basis: GST is reported when money moves. If customers paid faster than usual this period, GST payable can spike.
- A basis change mid‑year can create a one‑time jump. Confirm your setting and keep it consistent unless advised to change.
If you’re unsure which basis you’re registered for or whether a change is appropriate, speak with a small business accountant or BAS agent.
Common GST coding mistakes that inflate BAS
- Coding wages, super, loan repayments or owner drawings with GST.
- Not marking GST‑free or input‑taxed items correctly (e.g., fresh food, exports, residential rent, certain financial supplies).
- Claiming GST on entertainment/meal costs where credits are limited.
- Duplicates from unreconciled bank feeds or imported bills/invoices.
- Missing tax codes on large purchases (you then miss input credits).
Run a “by tax code” detail report and filter for the largest entries first. Fixing a few high‑value miscoded items often explains most of the difference.
PAYG instalments: why they went up and what you can do
PAYG instalments are prepayments of your income tax. The ATO can increase them after your latest tax return or via an annual uplift. If profit is down, you may be able to vary the rate or amount for the current BAS period.
- Check if this period’s PAYG instalment is the main reason your BAS rose.
- Consider a variation if current‑year profit is genuinely lower. Keep support for your estimate and be aware of potential interest if varied too low.
- If unsure, get advice from a tax accountant before you vary.
Best next steps
- Identify which component (GST, PAYG withholding, PAYG instalment) moved most.
- Drill into the transactions and fix any obvious coding errors.
- Decide whether to lodge now and amend later, or to seek an agent extension.
- If PAYG instalments are the driver and profit is lower, consider a variation with advice.
- Improve your process for next time: tighter reconciliations, clear GST coding rules, and earlier reviews before the due date. See Best Way to Prepare BAS.
If you want a guided review, compare BAS agent services, bookkeeping, and tax support to choose the right level of help.
Frequently asked questions
Why is my BAS higher than expected?
It’s usually a combination of higher taxable sales, fewer claimable purchases, cash vs accrual timing, increased payroll withholding, or an uplifted PAYG instalment. Run GST and payroll reports for the period, compare to last period, and review PAYG instalments on the BAS.
Could a cash vs accrual mismatch be the cause?
Yes. On accrual, GST is reported when you issue/receive invoices. On cash, it’s when money moves. Faster customer payments, slower supplier payments, or a basis change can all shift your BAS higher.
Why did my PAYG instalment jump?
The ATO may have increased your instalment based on your latest tax return or an uplift. If current profit is lower, you can consider a variation, ideally with input from a tax accountant.
What GST coding errors commonly inflate BAS?
Applying GST to wages, bank fees, loan repayments, owner drawings, or GST‑free items; missing GST on large purchases; and duplicated entries from unreconciled bank feeds are all common issues.
Should I lodge on time or wait?
Lodging on time avoids late penalties and interest. If you need more time, a BAS agent may help you access extended deadlines. You can amend a lodged BAS if you find errors later.
Who should I speak to?
For GST coding and BAS preparation, contact a BAS agent or bookkeeper. For PAYG instalment strategy and tax, speak with a tax accountant.