Question 1

How do I calculate sales tax on an invoice?

Accepted Answer

Multiply the net (pre-tax) amount by the tax rate as a decimal. For a $1,000 invoice at 7.25%, the tax is $1,000 × 0.0725 = $72.50, and the gross total is $1,072.50. This calculator does it automatically and formats the line for you to paste into the invoice.

Question 2

What is a reverse VAT calculator?

Accepted Answer

A reverse VAT calculator pulls the tax out of a price that already includes it. The formula is net = gross / (1 + rate/100). For a £120 total at 20% UK VAT, net = £120 / 1.2 = £100, and the VAT is £20. Use the "Extract tax from gross" mode for this.

Question 3

What's the difference between sales tax, VAT, and GST?

Accepted Answer

They're all consumption taxes added to invoices, but the mechanics differ. US sales tax is charged once at the point of sale, set at the state and local level. VAT (UK, EU) and GST (Canada, Australia, NZ, India) are charged at every step of the supply chain, with businesses reclaiming the tax they paid on inputs. The math on a single invoice line is the same — multiply by the rate.

Question 4

Are the US state rates the full sales tax rate?

Accepted Answer

No. The presets show the state base rate only. US combined sales tax also includes county and city additions, so the actual rate at a given ZIP code can be 1–4% higher. Look up the specific combined rate for your client's address and override the percentage in the calculator.

Question 5

What VAT rate should I use for an EU client?

Accepted Answer

If you're VAT-registered and selling B2B inside the EU, the reverse-charge mechanism usually applies and you invoice 0% VAT with a note. For B2C or domestic sales, use the rate of the customer's country (Germany 19%, France 20%, Spain 21%, Italy 22%, Ireland 23%, etc.). Pick the relevant preset or check with your accountant before invoicing.

Question 6

Should I add tax on top or include it in my price?

Accepted Answer

Most B2B invoices in the UK, EU, Canada, and Australia show the net price with tax added on a separate line — that's what business buyers expect, and it makes their bookkeeping clean. B2C pricing (especially online) often quotes the gross figure. Use the forward mode for the first, the reverse mode for the second.

Question 7

Why does my tax amount come out one cent off?

Accepted Answer

It's a rounding artifact. Calculating tax on the net and then rounding gives a slightly different total than calculating gross first and rounding backwards. This calculator rounds to two decimals on the displayed values but uses the full precision internally, which matches what most accounting platforms (QuickBooks, Xero, FreshBooks) do.

Question 8

Is this a substitute for tax advice?

Accepted Answer

No. This is a math tool. Tax rates change, exemptions apply, B2B vs B2C rules differ, and country-of-supply rules for digital services are their own topic. Use the calculator to handle the arithmetic, then confirm the rate and treatment with your accountant or local tax authority.

Sales Tax Calculator

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