GST on $300
Both answers, because "GST on $300" means two different things depending on whether that figure already includes GST.
How much GST is on $300?
- If $300 is before GST: GST is $45.00 and the total becomes $345.00.
- If $300 already includes GST: the GST portion is $39.13 and the price before GST is $260.87.
- Working: $300.00 × 1.15 = $345.00 · $300.00 ÷ 23 × 3 = $39.13
$300, worked both ways
| Treating $300 as… | GST | Ex GST | Inc GST |
|---|---|---|---|
| a price before GST | $45.00 | $300.00 | $345.00 |
| a total that includes GST | $39.13 | $260.87 | $300.00 |
| an Australian price at 10% | $30.00 | $300.00 | $330.00 |
The two NZ rows are the ones people mix up. Charging $45.00 of GST on an invoice whose total is meant to be $300 would leave you $5.87 short once Inland Revenue takes its cut — the GST inside $300 is only $39.13.
The two calculations
Adding GST to a GST-exclusive price.
Finding the GST already inside a total.
Stripping GST out to get the ex-GST price.
Taking 15% of a GST-inclusive figure is the common error — it overstates the GST every time. Full guide, with the registration rules and the $60,000 threshold →
Do the next bit too
The number is the easy part. These take it the rest of the way.
Make the invoice
Turn this figure into a compliant GST tax invoice with your logo and download the PDF. The amount carries across automatically.
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The rest of the toolkit
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