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.