Capital Gains Tax Calculator

This calculator estimates UK capital gains tax by comparing sale proceeds with purchase cost, allowable costs, annual allowance, and the tax rate you enter.

Capital gains tax is often relevant when selling investments, second homes, business assets, cryptoassets, or other chargeable assets. The taxable gain is not usually the full sale price; it is the gain after cost basis, allowable costs, reliefs, and allowances.

Use this for planning and comparison only. Actual tax can vary because of asset type, ownership history, reliefs, losses, residency, reporting deadlines, and current HMRC rules.

Suppose you bought an investment for £20,000 and later sold it for £32,000. The raw gain is £12,000. If you had £1,000 of allowable costs, the gain falls to £11,000.

If an annual exempt amount applies, only the gain above that allowance is taxable. For example, with a £3,000 allowance, the taxable gain would be £8,000. At a 20% rate, estimated capital gains tax would be £1,600.

The key point is that the sale price alone does not tell you the tax bill. Purchase cost, costs of disposal, losses, allowances, and reliefs can all change the result.

A gain is usually the difference between what you received for the asset and what it cost you, after allowable adjustments. Allowable costs can include some purchase costs, selling fees, and improvement costs, depending on the asset and rules.

Losses can sometimes reduce taxable gains, but the treatment depends on whether the loss is allowable and whether it has been reported correctly. Timing matters too, especially near the end of a tax year.

One mistake is calculating tax on the full sale price instead of the gain. Another is forgetting costs, previous losses, ownership shares, or changes in annual allowances. Property disposals may also have different reporting deadlines from other assets.

Before selling a large asset, it can be worth modelling the gain, checking whether any reliefs apply, and understanding when tax needs to be reported and paid. This calculator gives a quick estimate, not a substitute for tax advice.

Use this calculator when the disposal can be reduced to sale price, purchase price or cost basis, allowable costs, annual exempt amount, asset type, and basic versus higher/additional rate.

It is useful for quick UK CGT planning on shares, funds, cryptoassets entered as other assets, and residential property where you already know the broad rate category.

The calculator does not model private residence relief, business asset disposal relief, carried-forward losses, part disposals, non-resident rules, or reporting deadlines.

Use tax bracket calculator or uk income tax calculator alongside it when income level affects which CGT rate may apply.

Label saved scenarios with the tax year, asset type, allowance, and income-tax band assumption so you do not mix rate assumptions later.

Calculating tax on the full sale price instead of the gain after purchase cost and allowable costs.

Using the annual exempt amount twice when only the remaining allowance is available.

Applying the wrong asset type. Residential property and other assets use different rates in this simplified model.

Assuming basic-rate CGT applies without checking how the gain stacks on top of income.

Expecting the calculator to handle reliefs, losses, ownership shares, or deadlines automatically.

Example: sell an asset for £50,000, with a purchase cost of £30,000, £1,000 of allowable costs, and a £3,000 annual exempt amount.

The gain before allowance is £19,000. After the allowance, £16,000 is taxable in the simplified model.

If the selected rate is 20%, estimated CGT is £3,200. If the asset is residential property and the selected band uses 24%, the estimated tax changes.

Change one input at a time — sale price, purchase price, allowable costs, allowance, asset type, or band — so the reason for the tax movement stays clear.

Use tax bracket or uk income tax first if you are unsure whether the basic or higher/additional CGT rate should apply.

Use stock profit for pre-tax trade profit after buy and sell fees, then use this page only when the question becomes UK CGT.

Use capital gains tax us for US federal capital gains intent; this page is UK-focused.

For property disposals, pair this with professional guidance if private residence relief, letting relief, non-residence, or the residential property reporting deadline matters.

Check purchase records, sale statements, platform fees, legal fees, improvement costs, and any previous loss records before treating the gain as final.

Check whether the annual exempt amount has already been used by another disposal in the same tax year.

Check whether a property, cryptoasset, or business disposal has special treatment that is outside this simplified calculator.

Rerun this capital gains tax calculator when sale price, costs, income-tax band, annual exempt amount, or asset classification changes.

Recheck before selling if the disposal is close to a tax-year boundary, because timing can affect allowance use and reporting.

If this estimate differs from tax software or an adviser, trace gain, costs, allowance, reliefs, and rate choice separately rather than forcing the final tax number to match.