hmrc capital gains tax calculator

How this HMRC capital gains tax calculator works

This tool helps you estimate how much Capital Gains Tax you might owe when you sell an asset at a profit. In plain English, it takes your gain, subtracts allowable costs and losses, applies your annual exempt amount, and then taxes the remaining amount at the rates that normally apply to your situation.

The output gives a useful planning number. If you are making a major disposal (especially property, business assets, or complex investments), you should still check HMRC guidance or speak to a qualified adviser before filing.

Quick CGT process (UK)

1) Work out your gain

Your gain is usually:

• Sale proceeds
• Minus purchase cost
• Minus allowable acquisition and disposal costs
• Minus eligible capital improvement costs

If the result is negative, you made a capital loss rather than a gain.

2) Deduct capital losses and annual exempt amount

Capital losses can reduce taxable gains. After losses, you apply the annual exempt amount (AEA), if available. For 2024/25 and 2025/26 this calculator uses an AEA of £3,000 for individuals.

3) Apply the correct tax rate bands

CGT has lower and higher rates. How much of your gain falls into each rate depends on your taxable income and how much basic-rate band you have left.

• Other assets: usually 10% (lower) and 20% (higher)
• Residential property: usually 18% (lower) and 24% (higher from 2024/25)

What each input means

Sale proceeds

The amount you actually received for the asset. This is your disposal value before deducting costs.

Purchase cost

What you paid for the asset when you bought it (or market value in some special cases).

Allowable buying/selling costs

These are direct transaction costs linked to acquiring or selling the asset, such as legal fees, broker fees, and (for property) stamp duty on acquisition where applicable.

Improvement costs

Capital improvements can be deductible if they add value to the asset and are not routine repairs. For example, an extension to a property may count; repainting usually does not.

Capital losses

Include allowable losses you can set against gains. Some losses may need to be reported to HMRC first before they are available for set-off.

Taxable income

This determines how much of your gain can still use lower CGT rates. Higher taxable income typically means more gain gets taxed at the higher CGT rate.

Example calculation

Suppose you sell shares for £100,000 that cost £60,000 to buy, with £2,000 total buying/selling fees, no improvements, £3,000 losses, and taxable income of £25,000 (after personal allowance).

• Initial gain: £100,000 - £60,000 - £2,000 = £38,000
• After losses: £38,000 - £3,000 = £35,000
• After AEA (£3,000): £32,000 taxable gain
• Basic-rate band left: £37,700 - £25,000 = £12,700
• £12,700 taxed at 10%, remaining £19,300 taxed at 20%

Estimated CGT = £1,270 + £3,860 = £5,130.

Important things this estimate does not fully cover

• Private Residence Relief calculations for your main home
• Business Asset Disposal Relief (10% rate conditions)
• Trusts, companies, and non-resident specific rules
• Complex share matching rules (same-day / 30-day / section 104 pool)
• Gifts, connected persons, and market-value substitutions
• Interaction with Scottish income tax bands in advanced edge cases

Reporting and payment deadlines

If you sell UK residential property and CGT is due, you may need to report and pay within the HMRC property reporting deadline (often 60 days from completion). For other assets, gains are usually reported through self assessment by the normal annual deadline.

Ways people legally reduce CGT

• Use annual exemptions each year where possible
• Offset registered capital losses
• Transfer assets to a spouse/civil partner before disposal (where suitable)
• Use tax wrappers like ISAs and pensions for future growth
• Time disposals across tax years if practical

Always confirm strategy suitability for your personal circumstances.

Final note

This HMRC capital gains tax calculator is designed for speed and clarity. It gives a strong planning estimate for many common situations, but it is not a substitute for your actual tax return calculation or tailored advice.