Calculate GST inclusive/exclusive, track quarterly totals, and identify GST-free items
Preparing BAS every quarter? Calculate your GST in seconds with our free ATO-compliant calculator.
Goods and Services Tax (GST) is a 10% tax applied to most goods and services sold in Australia. As a business registered for GST, you collect GST from customers and pay GST on business purchases, reporting the net amount to the ATO via your Business Activity Statement (BAS) every quarter.
Key concept: Your quarterly BAS reports the difference between GST collected (from sales) and GST paid (on purchases). If you collected more than you paid, you owe the ATO. If you paid more, you receive a refund.
The price includes GST. This is what consumers see.
Example: Item priced at $110
• Base price: $100
• GST (10%): $10
• Total: $110 inc GST
The price excludes GST. Common in B2B transactions.
Example: Item priced at $100
• Base price: $100
• GST (10%): $10
• Total: $110 inc GST
💡 Quick conversion formulas:
• Add GST: Multiply by 1.1 (e.g., $100 × 1.1 = $110)
• Remove GST: Divide by 1.1 (e.g., $110 ÷ 1.1 = $100)
• Calculate GST component: Divide inclusive price by 11 (e.g., $110 ÷ 11 = $10)
Not everything attracts GST. Some goods and services are GST-free, meaning you don't charge GST on sales and can't claim GST credits on related purchases. Common GST-free items include:
⚠️ Prepared meals, restaurant food, and confectionery are taxable
⚠️ Cosmetic procedures and over-the-counter supplements are taxable
⚠️ Recreational courses and hobby classes are taxable
⚠️ Exported services must be consumed outside Australia
📚 Important: If you sell GST-free items, you can't claim GST credits on related business purchases. Check the ATO website for a complete list of GST-free and input-taxed supplies.
Most small businesses lodge BAS quarterly. Your lodgement dates depend on your accounting method:
| Quarter | Period | Due Date |
|---|---|---|
| Quarter 1 | July – September | 28 October |
| Quarter 2 | October – December | 28 February |
| Quarter 3 | January – March | 28 April |
| Quarter 4 | April – June | 28 July |
💡 If using a registered tax or BAS agent, you may have extended lodgement dates
Small Retail Business (Q1 July–September):
Total sales: $55,000 (inc GST)
GST collected: $55,000 ÷ 11 = $5,000
Total purchases: $33,000 (inc GST)
GST paid: $33,000 ÷ 11 = $3,000
Net GST Payable: $5,000 - $3,000 = $2,000
✅ This business owes $2,000 to the ATO for Quarter 1
Don't report GST on GST-free items (basic food, health services, exports). Only include taxable sales in 1A and purchases in 1B.
You can only claim GST credits on purchases related to your business. Personal expenses (even if paid from business account) are not claimable.
Late BAS lodgement incurs penalties. Set calendar reminders for 28th of the month following quarter end (or your agent's extended deadline).
Convert between GST-inclusive prices (what customers pay) and GST-exclusive amounts (your base price). Enter any amount and instantly see:
Estimate your BAS GST obligation by entering total sales and purchases for the period. The calculator shows:
Example: Product costs $100 (ex GST)
• GST amount: $100 × 10% = $10
• Price including GST: $100 + $10 = $110
Quick formula: Multiply by 1.1 (e.g., $100 × 1.1 = $110)
Example: Customer paid $110 (inc GST)
• Base amount: $110 ÷ 1.1 = $100
• GST component: $110 - $100 = $10
Quick formula: Divide by 11 to get GST (e.g., $110 ÷ 11 = $10)
Example: Quarter sales $55,000 (inc GST), purchases $33,000 (inc GST)
• GST collected: $55,000 ÷ 11 = $5,000
• GST paid: $33,000 ÷ 11 = $3,000
• Net GST payable: $5,000 - $3,000 = $2,000
To extract GST from an inclusive price, divide by 11, not multiply by 0.1. Example: $110 inc GST → GST is $110÷11=$10, not $110×0.1=$11.
Some items are GST-free (basic food, some medical, education). Don't include these in your GST calculations unless you're certain they attract GST.
Always clarify whether amounts are GST-inclusive or exclusive. Mixing them up leads to incorrect BAS reporting and potential penalties.