Percentages
Tax – Calculating Percentages on Goods and Income
Tax is a compulsory payment collected by governments on goods, services, income, and transactions. Understanding how tax is calculated as a percentage is essential for everyday life — from shopping to payslips.
Value Added Tax (VAT) — the model behind the UK's 20% standard rate used in the examples below — was first introduced in France in 1954 as taxe sur la valeur ajoutée, designed to collect tax at each stage of production rather than only at the final sale. It has since been adopted by more than 160 countries worldwide, usually under the name VAT or GST (Goods and Services Tax). Because tax rates and thresholds change with government policy, being able to calculate tax-inclusive and tax-exclusive prices confidently is a skill that stays useful regardless of what the current rate happens to be.
Types of Tax
| Tax Type | What It Applies To | Typical Rate (UK example) |
|---|---|---|
| VAT (Value Added Tax) | Most goods and services | 20% standard rate |
| Income Tax | Earnings above a threshold | Various bands (20%, 40%, 45%) |
| Council Tax | Residential properties | Varies by local authority |
| Stamp Duty | Property purchases | Varies by price band |
Calculating Tax on a Purchase
Tax Amount = Tax Rate% times Original Price / 100. Total Price = Original Price plus Tax Amount. Or: Total = Original times (1 + Tax%/100).
Worked Examples
VAT = 20% of 350 = 70. Total price = 350 + 70 = 420. Or: 350 times 1.20 = 420.
480 = pre-tax price times 1.20. Pre-tax = 480 / 1.20 = 400.
Taxable income = 30,000 - 12,570 = 17,430. Tax = 20% of 17,430 = 3,486. Take-home = 30,000 - 3,486 = 26,514.
Tax-Inclusive vs Tax-Exclusive Prices
| Scenario | Calculation |
|---|---|
| Add tax to a price | Price times (1 + rate/100) |
| Find pre-tax from inclusive price | Inclusive price divided by (1 + rate/100) |
| Find how much tax was paid | Inclusive price minus pre-tax price |
Key Takeaways
- Tax is calculated as a percentage of the taxable amount.
- Total price (tax-inclusive) = pre-tax price times (1 + tax rate/100).
- To find the pre-tax price: divide the inclusive price by (1 + tax rate/100).
- Always check whether a quoted price includes or excludes tax.