Add GST Calculator (Calculate GST-Inclusive Price)
Add GST Calculator
How to add GST to a price
The formula is short.
- GST amount = Net price × 0.10
- GST-inclusive price = Net price × 1.10
- Verification: Net + GST = inclusive price
The reason we multiply by 1.1 is that the inclusive price is the original 100% plus 10% on top, which equals 110% – or 1.1 expressed as a decimal. Multiplying by 0.1 gives you the GST line on its own; multiplying by 1.1 gives you the full inclusive total in one step.
Worked example: a $250 invoice from a Brisbane tradie
Say a sole trader electrician quotes a homeowner $250 ex-GST for a power-point install. To convert that to a GST-inclusive figure for the tax invoice:
- Net price = $250
- GST = $250 × 0.10 = $25
- Inclusive total = $250 × 1.1 = $275
- Check: $250 + $25 = $275 ✓
The invoice shows three lines – a subtotal of $250, a GST line of $25 and a total of $275. The ATO requires both the GST amount and the inclusive total to appear on tax invoices over $82.50.
Adding GST to multiple line items
A real invoice rarely has one line. Here’s a four-line example for a small home-office fitout sourced from Officeworks:
| Item | Ex-GST | GST | Inc. GST |
| Standing desk | $700.00 | $70.00 | $770.00 |
| Office chair | $450.00 | $45.00 | $495.00 |
| Monitor arm | $180.00 | $18.00 | $198.00 |
| Cable tray | $50.00 | $5.00 | $55.00 |
| Total | $1,380.00 | $138.00 | $1,518.00 |
Two ways to get to the total: sum the ex-GST column and multiply by 1.1, or sum the inc-GST column directly. Both should give $1,518. In Excel or Google Sheets the formulas are:
- Total ex-GST: =SUM(B2:B5)
- Total GST: =SUM(B2:B5)*0.1
- Total inc-GST: =SUM(B2:B5)*1.1
Stick to per-line GST when the invoice mixes GST and GST-free items (more on that below) – pooling everything into a single multiplication breaks the moment a GST-free item appears.
When to add GST vs charge a GST-free price
Two questions decide it.
Are you registered for GST? If your business turnover is below the $75,000 threshold (or $150,000 for non-profits) and you haven’t voluntarily registered, you don’t add GST. You also can’t claim GST credits. Rideshare and taxi drivers are the exception – they must register from the first dollar regardless of turnover.
Is the supply itself taxable? Even if you’re registered, certain supplies don’t attract GST. The main GST-free categories are basic food (a loaf of bread from Coles), most education services, most health and medical supplies and exports. Input-taxed supplies – financial services and residential rent – also sit outside the GST net but with a different mechanism: no GST charged, no credits claimed.
So a GST-registered café selling cooked meals charges GST, but the same café selling unprocessed bread and milk doesn’t. Both need to appear correctly on the receipt.
GST inclusive vs GST exclusive on quotes
The ambiguity trap is the line item that just says ‘$5,000’. Is that the GST-inclusive price the customer pays, or the ex-GST quote you’ll add 10% to?
Two rules of thumb:
- Quotes to consumers (B2C) must show the GST-inclusive price under ACCC pricing rules. A retail Bunnings price tag is always inclusive.
- Quotes to businesses (B2B) are conventionally GST exclusive, with ‘plus GST’ or ‘+ GST’ written next to the figure. The invoice that follows then breaks out the GST line.
If you’re not sure which side of the fence the customer sits on, write the figure both ways: ‘$5,000 ex GST ($5,500 inc. GST)’. That removes the argument before it starts.
Common mistakes
- Charging GST when you’re not registered. Issuing an invoice with a GST line implies registration. The ATO can recover that 1/11 from you whether or not you actually collected it from the customer.
- Missing the $75,000 threshold mid-year. Once your rolling 12-month turnover crosses $75,000, you have 21 days to register. Sole traders often miss this because they’re tracking financial-year totals instead of rolling totals.
- Mixing GST and GST-free items without itemising. A bakery invoice for $40 of bread and $30 of cooked sandwiches needs the cooked portion split out – it’s the only part that attracts GST. Bundling everything together overstates the GST collected.
- Adding GST to input-taxed supplies. Residential landlords sometimes try to add GST on rent. They can’t.
- Per-line vs total rounding. Xero and MYOB round at the line level by default; some manual invoices round on the total. The two methods can drift by a cent or two on long invoices, which the ATO accepts as long as you’re consistent.
Related calculators
- GST Calculator (homepage) – the all-in-one add and reverse tool
- Reverse GST Calculator – divide by 11
- GST Inclusive Calculator – find the GST in a total you’ve already been charged
- How to add GST to an invoice – the ATO’s tax invoice rules in plain English
FAQs
How do you add 10% GST to a price?
Multiply the ex-GST price by 1.1. So a $200 ex-GST price becomes a $220 GST-inclusive price ($200 + $20 GST). Multiplying by 0.1 gives you the GST line ($20) by itself.
What is the formula to add GST in Australia?
The formula is Net × 1.1 = Gross, or Net × 0.1 = GST line. The 1.1 covers the original 100% plus the 10% GST in one step, which is why it’s the fastest way to get to the inclusive total.
Should I add GST to my invoice as a sole trader?
Only if you’re registered for GST. Registration is mandatory once your rolling 12-month turnover crosses $75,000, or from day one if you drive rideshare or taxi. Below that threshold you can register voluntarily – it lets you claim GST credits on business expenses, but it also means you have to add GST to every taxable sale.
How do I calculate the GST-inclusive price from net?
Multiply the net price by 1.1. A $99 net price becomes a $108.90 inclusive price. If the inclusive figure needs to land on a clean dollar amount, adjust the net price first rather than rounding the multiplier.
Do I need to add GST if I’m under the $75,000 threshold?
No, unless you’ve voluntarily registered. If you’re not registered, charging a ‘GST line’ on your invoice is a problem – the ATO treats any invoice that implies GST as if you were registered, and can claim that 1/11 portion back.
What’s the difference between adding GST and including GST?
Adding GST means starting with an ex-GST figure and multiplying by 1.1 to find the price the customer pays. Including GST means the price already has GST baked in. To extract the GST from an inclusive price, you’d run the reverse calculation – divide by 11.
The calculators and guides on gstcalculator.net.au are for general information only and do not constitute tax, financial, or legal advice. Consult a registered tax agent for advice specific to your situation.