GST Calculator for BAS Quarterly Lodgement
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.
This is the net amount you need to pay to the ATO for this period.
Calculation Breakdown:
Maximize Your 2026 Refund
You owe $6,818.18 GST to the ATO. Upload receipts to track business expenses and reduce your GST liability.
💼 Save Your Business Profile
Save your business details to pre-fill future GST calculations
How to Use This Calculator
Enter Your Details
- Annual revenue (GST inclusive/exclusive)
- Annual expenses (GST inclusive/exclusive)
- Select GST registration status
- Choose quarterly or monthly BAS
Review Results
- GST collected on sales
- GST paid on purchases
- Net GST payable/refundable
- Export as PDF or CSV
Understanding GST for Small Business Owners
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.
GST Inclusive vs GST Exclusive Explained
GST Inclusive
The price includes GST. This is what consumers see.
Example: Item priced at $110
• Base price: $100
• GST (10%): $10
• Total: $110 inc GST
GST Exclusive
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)
GST-Free Items in Australia
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:
Basic Food Items
- • Bread, milk, eggs, meat, fish
- • Fresh fruit and vegetables
- • Cereals, pasta, rice
- • Cooking ingredients (flour, sugar, oil)
⚠️ Prepared meals, restaurant food, and confectionery are taxable
Health & Medical
- • Doctor and specialist consultations
- • Hospital services
- • Prescription medicines
- • Disability aids and medical equipment
⚠️ Cosmetic procedures and over-the-counter supplements are taxable
Education
- • School fees and university tuition
- • Pre-school and childcare
- • Courses leading to formal qualifications
- • Textbooks and course materials
⚠️ Recreational courses and hobby classes are taxable
Exports & International
- • Goods exported from Australia
- • International transport and freight
- • Services consumed outside Australia
- • Precious metals (gold, silver, platinum)
⚠️ 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.
BAS Quarterly Lodgement: What You Need to Know
When to Lodge Your BAS
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
Real Example: Quarterly BAS Calculation
Small Retail Business (Q1 July–September):
📈 Sales (GST Collected)
Total sales: $55,000 (inc GST)
GST collected: $55,000 ÷ 11 = $5,000
📉 Purchases (GST Paid)
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
Common BAS Lodgement Mistakes
❌ Including GST-free sales in BAS calculations
Don't report GST on GST-free items (basic food, health services, exports). Only include taxable sales in 1A and purchases in 1B.
❌ Claiming GST on private expenses
You can only claim GST credits on purchases related to your business. Personal expenses (even if paid from business account) are not claimable.
❌ Missing the lodgement deadline
Late BAS lodgement incurs penalties. Set calendar reminders for 28th of the month following quarter end (or your agent's extended deadline).
GST Calculator Guide
GST Inclusive/Exclusive
Convert between GST-inclusive prices (what customers pay) and GST-exclusive amounts (your base price). Enter any amount and instantly see:
- • GST component (10% of exclusive amount)
- • Base amount (excluding GST)
- • Total including GST
BAS GST Calculation
Estimate your BAS GST obligation by entering total sales and purchases for the period. The calculator shows:
- • GST collected on sales
- • GST paid on purchases
- • Net GST payable (or refundable)
Common GST Calculations Explained
Adding GST (10% to price)
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)
Removing GST (reverse calculation)
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)
Calculating BAS Net GST
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
Common GST Mistakes to Avoid
❌ Multiplying by 0.1 instead of dividing by 11
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.
❌ Forgetting GST-free items
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.
❌ Mixing inclusive and exclusive amounts
Always clarify whether amounts are GST-inclusive or exclusive. Mixing them up leads to incorrect BAS reporting and potential penalties.
When to Use This Calculator
✅ Perfect For:
- • Converting prices for quotes and invoices
- • Estimating BAS GST before lodgement
- • Checking supplier invoices for GST accuracy
- • Planning cashflow for GST payments
- • Quick GST calculations during bookkeeping
⚠️ Note:
- • This is an estimate tool, not official BAS lodgement
- • Always verify with your accounting software
- • Consult your accountant for complex GST scenarios
- • Check ATO guidance for GST-free items