Sales Tax, VAT and GST: How They Work (Conceptually)

Consumption taxes are charged when goods or services are bought rather than on income. In the broadest terms:

• A retail sales tax is charged only on the final sale to the consumer. Businesses buying goods for resale generally do not pay it.
• Value-added tax (VAT) and goods and services tax (GST) are charged at each stage of production and distribution. Each business charges tax on its sales, deducts the tax it paid on its purchases (an input credit), and remits the difference. The final consumer bears the whole tax, because the consumer cannot claim a credit.

Terminology varies by country, and some places combine several levels of tax. The ratios below work for any single rate you enter.

If the price is tax-exclusive (net), add the rate:

gross = net × (1 + rate)

At a rate of 10%, a net price of $100 gives $110, with $10 of tax. This is the usual way retail prices are shown in places that add tax at the till.

If the price is tax-inclusive (gross), divide by (1 + rate) to find the net amount:

net = gross ÷ (1 + rate), and tax = gross − net

At 10%, a tax-inclusive price of $110 is a net price of 110 ÷ 1.10 = $100, so the tax is $10. A common error is to take 10% of $110 and subtract $11, which gives $99 and understates the net price. The tax portion of a tax-inclusive price is gross × rate ÷ (1 + rate): 110 × 0.10 ÷ 1.10 = $10.

Another way to remember it: the tax is rate ÷ (1 + rate) of the gross price. At 20% that is one-sixth, so a $60 tax-inclusive price contains $10 of tax and has a $50 net price.

Assume a single 10% rate and a product passing through two businesses to a consumer.

• A manufacturer sells to a retailer for $100 net. It charges $10 tax and remits $10 (it paid no input tax in this simplified example).
• The retailer sells to a consumer for $150 net. It charges $15 tax, and claims a $10 credit for the tax it paid, so it remits $15 − $10 = $5.
• Total tax collected by the government: $10 + $5 = $15. That equals 10% of the final $150 net price, paid by the consumer.

The value added at each stage ($100 by the manufacturer, $50 by the retailer) is taxed once, which is where the name comes from. This is a simplification: real systems have exemptions, zero rates, reduced rates, registration thresholds and special schemes.

Some goods and services are taxed at a lower rate, at zero, or exempted. In many systems “zero-rated” and “exempt” differ: a zero-rated seller can still claim input credits, while an exempt seller generally cannot. The rules differ by jurisdiction, so use the calculator with the rate your tax authority publishes for the item you are pricing.

When tax, tip and discount are combined, the order affects the answer. A discount applied before tax lowers the taxable amount. A tip calculated on a tax-inclusive total is higher than one calculated on the pre-tax subtotal. Check which basis applies, whether to a shop’s policy or a group’s agreement.

Business invoices often list a net amount, the tax and a gross total per line. If an invoice covers items taxed at different rates, compute each line separately and sum, rather than applying an average rate to the whole. The GST Invoice Split Calculator does this arithmetic for a single rate or a split.

• Subtracting the rate from a tax-inclusive price instead of dividing by (1 + rate).
• Applying a rate that does not match the item (for example, a standard rate to a reduced-rate good).
• Mixing tax-inclusive and tax-exclusive prices when comparing sellers.
• Forgetting that some items or businesses are exempt.
• Treating a calculator result as a tax filing; always rely on your tax authority’s guidance and official invoices.

The GST / VAT Calculator adds or removes tax at a rate you type. The Sales Tax Calculator and the Add / Remove Sales Tax tool do the same for retail sales tax. Nothing on this site states a current official rate for any country; look up the one that applies to you.