How to use this Quarterly BAS Estimator

Purpose:
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This tool estimates your total BAS payment across the five most common lines on a standard quarterly activity statement. It is designed for Australian SMEs lodging on a quarterly cycle, which covers most businesses with GST turnover under $20 million. Enter your figures from Xero, MYOB or QuickBooks, toggle on the sections that apply to your business, and the tool calculates what you will owe (or be refunded by) the ATO.The estimator is most accurate when you use exact figures pulled from your accounting software. Where you do not have an exact number, the tool offers estimate modes that give you a rough ballpark for cashflow planning. These estimates are not a substitute for the figures on your actual activity statement.

Tips for Ongoing Use:
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Bookmark this page (Ctrl+D or Cmd+D) and run the numbers every quarter, three to five business days before your BAS is due. Pull your figures from Xero's BAS Preview report, MYOB's GST return report or your accounting software's equivalent. For cashflow planning, run the tool at the end of each month during the quarter so you can set aside cash as you go, rather than scrambling on BAS day.

Understanding your full BAS obligation:
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Most business owners think of BAS as "the GST bill". It is not. A typical quarterly BAS for a profitable trading business covers five separate obligations, all lodged and paid together:

1. Net GST (1A minus 1B)
‍GST is the component everyone knows about. You collect GST at 10% on taxable sales (reported at label 1A) and claim credits for the GST you paid on business purchases (label 1B). The difference is what you pay or claim as a refund. For most trading businesses, net GST is usually between 5% and 9% of quarterly sales once purchases, wages (GST-free) and other costs are factored in.

2. PAYG withholding (W1, W2)
‍If you pay employees, you deduct PAYG tax from their wages each pay cycle and hold it on the ATO's behalf. That tax is remitted to the ATO quarterly through your BAS. Label W1 is total gross wages paid, W2 is total tax withheld. W2 is what gets added to your BAS payment. For a business with $85,000 of quarterly wages and average PAYG withholding rates, this typically adds $15,000 to $20,000 to the BAS.

3. Income tax instalment (PAYG-I, label T7)
‍This is the line most business owners underestimate. PAYG instalments are quarterly prepayments of your company or personal income tax, set by the ATO based on your last tax return. For a profitable business, this is often the single biggest line on the BAS. A company paying $50,000 in annual income tax instalments is paying $12,500 each quarter on top of GST and PAYG withholding. The ATO sends you the amount to use on your activity statement, or you can calculate it using your personalised instalment rate applied to quarterly income.

4. FBT instalment (F1)
‍If you provide fringe benefits like company cars, entertainment or private-use phones, and your prior-year FBT liability was above a threshold, the ATO requires you to pay FBT in quarterly instalments. The ATO sends a notice with the instalment amount to include on your BAS. Many SMEs do not pay FBT quarterly, in which case this section does not apply.

5. Fuel Tax Credits (7D)
‍If your business uses diesel or petrol in vehicles, machinery or equipment, you may be entitled to claim Fuel Tax Credits. The rates vary by fuel type and how the fuel is used (on-road heavy vehicle, off-road machinery, agricultural use). FTC reduces your total BAS payment.

Quarterly BAS due dates:
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1The ATO sets standard BAS due dates on the 28th day of the month after each quarter ends. Registered BAS Agents receive an additional four-week concession on Q1, Q3 and Q4. There is no extension on Q2 because Q2 already includes a concession for the Christmas period.

- Q1 (July to September): 28 October self-lodger, 25 November via BAS Agent
- Q2 (October to December): 28 February for both self-lodgers and BAS Agents
- Q3 (January to March): 28 April self-lodger, 26 May via BAS Agent
- Q4 (April to June): 28 July self-lodger, 25 August via BAS Agent

Due dates shift to the next business day if they fall on a weekend or national public holiday. Signing up to an agent the week the BAS is due does not get you the extension on that quarter.

Common BAS mistakes this estimator helps catch:
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This calculator aids in pricing exports competitively, managing import costs, and simplifying BAS reporting (e.g., G2 for GST-free exports, G10/G11 for imports). Explore Scale Suite’s finance services for expert GST support.

1. Underestimating the income tax instalment: 
‍The most common cashflow mistake we see is business owners putting aside cash for GST and wages tax but forgetting PAYG-I. A profitable company doing $300,000 quarterly profit at 25% company tax is paying $75,000 in instalments, every quarter. If you only budgeted for GST, that comes as a nasty surprise on the 28th.

2. Treating GST-free sales as taxable:
‍If you have a mix of GST-free, input-taxed and taxable sales, the estimate mode in this tool (which applies 10% GST to everything) will overstate your GST. Switch to exact mode and pull 1A and 1B directly from your accounting software.

3. Missing PAYG withholding on directors' wages:
‍Director salaries are subject to PAYG withholding like any other employee. If the director is being paid via the company payroll, that withholding goes in W2 alongside other staff. Missing this line understates the BAS and can trigger an ATO query.

4. Not claiming Fuel Tax Credits:
‍Businesses with diesel vehicles, machinery, farming operations or heavy road transport often fail to claim Fuel Tax Credits. This is money left on the table every quarter. If you have a fuel card or buy diesel for business use, check whether you qualify.

‍Quarterly BAS Estimator FAQ:
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Q: What is a BAS?
‍A Business Activity Statement (BAS) is the form Australian businesses lodge with the ATO to report and pay GST, PAYG withholding, PAYG income tax instalments, FBT instalments, Fuel Tax Credits and other indirect taxes. Most businesses lodge quarterly. Businesses with GST turnover above $20 million lodge monthly.

Q: Is this BAS estimator free?
‍Yes, the tool is completely free with no sign-up, no email capture and no download required. It is built by Scale Suite as a general resource for Australian SMEs.

Q. How accurate is the estimator?
‍Accuracy depends on the figures you enter. If you use exact mode for GST and pull your PAYG withholding, T7 and FBT figures directly from your ATO notices and accounting software, the total should match your actual BAS within a few dollars. Estimate modes (1/11th GST on totals, quarterly profit times company tax rate) are designed for cashflow planning, not lodgement. Always verify against your actual activity statement before paying the ATO.

Q. Why is the income tax instalment estimate only a ballpark?
‍The ATO calculates your PAYG income tax instalment using a personalised instalment rate based on your last tax return. This rate can be very different from a simple "25% or 30% of profit" calculation, especially if your business had a loss carried forward, tax offsets, or a significantly different prior year. The estimate mode is designed to give you a rough cashflow number, not your actual T7.

Q. Does the calculator work for sole traders and partnerships?
‍Partly. The GST, PAYG withholding and Fuel Tax Credits sections work for any business structure. The income tax instalment estimate mode uses company tax rates (25% or 30%), so sole traders and partnerships should use the "Use ATO amount" mode with their actual T7 from the ATO. Sole trader PAYG-I is calculated on personal marginal tax rates, which this tool does not attempt to model.

Q. Why does the tool give me an extra 4 weeks through a BAS Agent?
‍Registered BAS Agents receive a concessional lodgement program from the ATO, which gives an additional four weeks on Q1, Q3 and Q4 BAS. This is legitimate ATO policy designed to give agents time to prepare client work. To qualify, you must be registered as a client of the agent before the standard due date.

Q. What if I have GST-free or input-taxed sales?
‍Switch to exact mode and enter your actual 1A (GST on sales) and 1B (GST on purchases) directly from your accounting software. Estimate mode assumes 10% GST on every dollar of sales and every dollar of purchases, which will overstate your GST liability if you have meaningful GST-free income like exports, certain health and education services, or residential rent.

Q. What happens if I miss my BAS due date?
‍The ATO applies a Failure to Lodge (FTL) penalty of one penalty unit (currently $330) per 28-day period the BAS is late, capped at five units for small businesses ($1,650). On top of that, General Interest Charge applies at around 11% per annum on the outstanding amount, compounding daily. GIC is no longer tax-deductible as of 1 July 2025, so late BAS has become materially more expensive.

Q. Do I need to register for GST?You must register for GST if your annual turnover is $75,000 or more ($150,000 for not-for-profits), or if you drive a taxi or ride-share vehicle regardless of turnover. Below the threshold, registration is voluntary. Once registered, you must lodge BAS on your assigned cycle (monthly, quarterly or annually).

Q. Can Scale Suite lodge my BAS for me?
‍Yes. As a registered BAS Agent, Scale Suite prepares and lodges BAS for Australian SMEs, manages ATO correspondence, and provides the four-week lodgement concession on eligible quarters.

Q. Want help with your BAS?
‍Scale Suite is a Sydney-based embedded finance team for Australian SMEs. We prepare, review and lodge your BAS as your registered BAS Agent, manage ATO correspondence on your behalf, and give you an extra four weeks to pay on most quarters. CA-qualified, Xero Certified, and serving businesses across Sydney, Melbourne, Brisbane and Perth with packages starting from $1,500 per month and no lock-in contracts. Tax returns and income tax advice are handled by our registered Tax Agent partner, so you get a complete finance function in one place.

Disclaimer:
This tool provides an estimate only and does not constitute tax advice. Scale Suite is a registered BAS Agent (26298194), our scope covers BAS preparation and lodgement, GST, PAYG withholding and related BAS obligations. For income tax advice, annual returns, FBT returns and CGT matters we refer to registered Tax Agent partners. Scale Suite is not liable for any loss arising from reliance on this tool. Always verify your figures against your actual activity statement and the ATO's guidance before lodging.

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