Adding and Removing Tax
Adding tax is straightforward multiplication. Removing it is where people go wrong: you cannot subtract the percentage, because the tax was calculated on the smaller net figure, not on the gross total you are holding. You have to divide.
Remove: Net = Gross ÷ (1 + Rate ÷ 100)
Tax amount = Gross − Net
A UK invoice totals £150 including 20% VAT. The net amount is 150 ÷ 1.20 = £125, and the VAT is £25. Subtracting 20% from £150 would give £120 — wrong by £5, and a mistake that compounds across a whole ledger.
Sales Tax, VAT and GST
| System | Where | Shown in prices? |
|---|---|---|
| Sales tax | United States | Usually added at checkout |
| VAT | UK, EU and much of the world | Normally included in the shelf price |
| GST | Australia, Canada, India, NZ, Singapore | Usually included (Canada often adds it) |
This difference matters when comparing prices internationally: a US price is typically pre-tax and a European one post-tax, so the shelf numbers are not like-for-like.
Tax and Your Margins
Tax collected is not income. Calculating profit on tax-inclusive figures inflates both revenue and margin, and the gap is exactly the amount you owe the tax authority later. Strip tax out here first, then take the net figures to the margin calculator or the profit calculator. If you are also running promotions, apply the discount to the net price before adding tax back on.
Rates Change — Check Yours
This calculator deliberately does not guess your rate. US rates combine state, county and city components and differ by product; VAT and GST rates are revised by legislation, and reduced rates apply to categories like food, books and children's clothing. Enter the rate that applies to your transaction and the arithmetic will stay right no matter what changes.
In practice How a freelancer invoices correctly across borders
A designer agrees a fee of £2,000 with a UK client and must add 20% VAT: 2,000 × 1.20 = £2,400 on the invoice, of which £400 belongs to HMRC, not to her.
A month later a different client says "we can pay £1,800 including VAT". The temptation is to subtract 20% and quote £1,440 — which is wrong. Dividing gives the correct net fee: 1,800 ÷ 1.20 = £1,500, with £300 of VAT. Subtracting instead would have quietly cost her £60.
Her books use the £1,500, never the £1,800 — which is also the figure that belongs in a margin or profit calculation.
Frequently Asked Questions
How do I add sales tax to a price?
Multiply the net price by the tax rate divided by 100 to get the tax, then add it. On $80 at 8.25%: tax is $6.60 and the total is $86.60. Equivalently, multiply by 1.0825.
How do I remove VAT from a gross price?
Divide the gross price by (1 + rate ÷ 100) — do not subtract the percentage. At 20% VAT, a £120 gross price is £120 ÷ 1.20 = £100 net, with £20 VAT. Subtracting 20% instead would wrongly give £96.
What is the difference between sales tax, VAT and GST?
US sales tax is charged once, at the final sale, and is usually shown separately at checkout. VAT (Europe, UK) and GST (Australia, Canada, India, and others) are collected at each stage of the supply chain with businesses reclaiming what they paid, and displayed prices normally already include it. The arithmetic on a single transaction is identical.
Should I include tax when calculating profit margin?
No. Tax you collect belongs to the government, not the business, so it is neither revenue nor profit. Strip it out here and take the net figures to the margin calculator.
Why does the calculator not know my local tax rate?
Rates change constantly and vary by state, county, city and product category — a hard-coded table would be wrong somewhere within weeks. Enter your current rate and the result stays correct forever. Check your tax authority for the rate that applies to you.
Sources & Further Reading
- VAT rates applied in EU member states — European Commission, Taxation and Customs Union
- State and local sales tax rates — Tax Foundation
- VAT rates on goods and services — UK HM Revenue & Customs (GOV.UK)
Cite This Calculator
Using this calculator in an assignment, article or lesson? Copy a ready-made citation — or the link snippet if you're referencing it from a web page.
The CalculatorsGuide Editorial Team. (2026). Sales Tax & VAT Calculator. CalculatorsGuide. Retrieved from https://www.calculatorsguide.com/finance/sales-tax-calculator/