BAS Calculator Australia

A Business Activity Statement (BAS) is how Australian businesses report and pay GST to the ATO. The GST section is the most common part: you report the GST collected on sales (1A) and the GST credits on purchases (1B), and pay the difference (ATO — BAS due dates). The calculator above estimates the net GST payable or refund for any reporting period. To check an individual invoice amount, the GST Calculator adds or removes 10% GST from any amount.

How to Calculate Your BAS

The GST component of your BAS involves two key amounts:

1. Label 1A — GST on sales: The total GST you collected from customers on taxable sales during the period. If you sold $50,000 worth of goods and services (excluding GST), the GST on sales is $50,000 x 10% = $5,000.

2. Label 1B — GST on purchases: The total GST included in the price of business purchases you can claim as credits. If you spent $20,000 on business supplies (excluding GST), the GST on purchases is $20,000 x 10% = $2,000.

3. Net GST payable: 1A minus 1B. In this example: $5,000 - $2,000 = $3,000 payable to the ATO.

If your GST on purchases (1B) exceeds GST on sales (1A), the ATO owes you a refund. This commonly happens when a business makes large purchases (such as buying equipment) or when a significant portion of sales are GST-free or exported.

What BAS mistakes can cost you

The GST labels on BAS are simple, but mistakes get expensive quickly:

• Late payment exposure: If BAS is lodged or paid late, the ATO can charge interest on overdue amounts (ATO — BAS due dates).
• Cash-flow pain: Overstating 1A or missing 1B credits means paying more now and waiting for corrections later.
• Rework time: BAS errors usually mean extra reconciliation work before your next lodgement, especially when reconciling invoices vs cash receipts.

Using a quick pre-lodgement check with this calculator helps catch obvious 1A/1B mismatches before you lodge.

GST reporting methods

There are two methods for reporting GST on your BAS (ATO — How GST works):

• Cash basis: Report GST when you receive payment (for sales) or make payment (for purchases). Many smaller businesses use this method because it follows actual cash movement.
• Accrual basis: Report GST when you issue or receive an invoice, regardless of when payment occurs. This aligns more closely with standard accrual accounting records.

The method you choose affects the timing of your GST reporting, not the total amount. This calculator works with either method — enter the total sales and purchases for the period based on whichever method you use.

BAS Due Dates 2025-26

Late BAS lodgement can result in penalties from the ATO (ATO — BAS due dates). The following table shows the standard BAS due dates for the 2025-26 financial year.

Quarterly BAS due dates

If the due date falls on a weekend or public holiday, you have until the next business day.

Monthly BAS due dates

Monthly BAS is due on the 21st of the following month. For example, July 2025 BAS is due 21 August 2025. If you lodge electronically, you may receive an additional two weeks for some months.

Annual BAS

If you are eligible for annual GST reporting, your BAS is generally due when you lodge your income tax return.

In practice, businesses with GST turnover below $20,000,000 usually stay on quarterly reporting, while businesses at or above $20,000,000 generally move to monthly BAS reporting (ATO — GST reporting options).

GST Reporting Methods

Which method should you choose?

Cash basis is simpler and better for cash flow management. You only report GST when money actually changes hands. If a customer has not paid an invoice, you do not report the GST until they do.

Accrual basis aligns with standard accounting practices. You report GST based on invoices issued and received, regardless of payment. This gives a more accurate picture of GST obligations but can mean paying GST before you have received payment from customers.

Choose the method that matches how you track sales and purchases in your accounting records. The calculator works with either method because you enter the totals for the BAS period you are preparing.

Worked Example

Scenario: A property management business reports quarterly BAS. In Q2 (October to December 2025):

• Total sales (excluding GST): $85,000
• Total business purchases (excluding GST): $32,000

Calculation:

• GST on sales (1A): $85,000 x 10% = $8,500
• GST on purchases (1B): $32,000 x 10% = $3,200
• Net GST payable: $8,500 - $3,200 = $5,300

The business owes the ATO $5,300 for Q2, due by 28 February 2026.

Refund scenario: If the business made a large equipment purchase of $60,000 (ex-GST) in the same quarter:

• GST on purchases (1B): ($32,000 + $60,000) x 10% = $9,200
• Net GST: $8,500 - $9,200 = -$700 (refund)

The ATO would refund $700 to the business.

Common BAS Mistakes

1. Including GST-free sales in the GST calculation. If some of your sales are GST-free (for example, exports or basic food), do not include the GST-free portion when calculating label 1A. Only taxable sales attract GST.

2. Claiming GST credits on purchases related to input-taxed supplies. If you earn residential rental income (which is input-taxed), you generally cannot claim GST credits on expenses related to the rental property. The GST on property management fees, repairs, and insurance is a genuine cost.

3. Not reconciling BAS to accounting records. Your BAS GST figures should match your accounting software. Discrepancies may indicate missed transactions, double-counted invoices, or timing differences between cash and accrual methods.

4. Missing the due date. Late BAS lodgement or payment can lead to ATO follow-up and interest on overdue amounts (ATO — BAS due dates). If you cannot lodge on time, contact the ATO before the due date to request an extension.

5. Forgetting to report PAYG withholding. If you have employees, your BAS also includes PAYG withholding amounts. This calculator covers only the GST section — ensure you also report employee withholding on your actual BAS.

If you need a business-income tax estimate rather than a GST estimate, use the sole trader tax calculator to model income tax, Medicare levy, HELP repayments, and quarterly PAYG instalments. If you need employee withholding references, see the PAYG tax table guide.

BAS for Property Investors

Most individual property investors do not need to lodge a BAS. BAS is required only if you are registered for GST, which is mandatory when your business GST turnover reaches $75,000 per year (or $150,000 for non-profits) (ATO — Registering for GST).

Residential rental income is input-taxed, meaning no GST is charged on rent and no GST credits can be claimed on related expenses. Most individual landlords are not carrying on a business and are not required to register for GST.

However, if you operate a property management business, develop properties for sale, or earn commercial rental income, you may need to lodge BAS. Commercial property rent is a taxable supply, so GST applies to both the rent and the expenses.