Capital Gains Tax Calculator

A capital gains tax calculator works out the tax owed on the profit made from selling an asset such as a property, shares, or other investment. It is used by investors and property sellers in the UK to estimate their tax liability before disposal, plan the timing of sales, and understand how allowances and reliefs affect the final tax bill.

How to Use the Capital Gains Tax Calculator

1. Enter the sale proceeds (the amount you received for the asset).
2. Enter the original purchase price (the cost of the asset when you bought it).
3. Enter any allowable costs (solicitor fees, stamp duty on purchase, improvement costs for property).
4. Enter your income tax band (basic rate or higher/additional rate) as this affects the CGT rate.
5. Select the asset type (residential property, other assets).
6. Click calculate to see the taxable gain, annual exempt amount deduction, and estimated tax.

The Formula

Capital gain = Sale proceeds - (Purchase price + Allowable costs)

Taxable gain = Capital gain - Annual Exempt Amount (£3,000 for 2024/25 for individuals)

CGT rates for 2024/25:

For assets other than residential property:

• 18% (basic rate taxpayers, using remaining basic rate band)
• 24% (higher/additional rate taxpayers)

For residential property (not main home):

• 18% (basic rate taxpayers)
• 24% (higher/additional rate taxpayers)

Note: rates were changed in the October 2024 Autumn Budget. The main residence exemption (Private Residence Relief) eliminates CGT on the sale of your only or main home.

Real-World Example

You sell a rental property for £320,000. You bought it for £210,000 in 2015. Allowable costs: £5,000 legal fees on purchase, £8,000 extension in 2018. You are a higher-rate taxpayer.

Capital gain: £320,000 - (£210,000 + £5,000 + £8,000) = £97,000

Taxable gain: £97,000 - £3,000 (Annual Exempt Amount) = £94,000

CGT at 24% (residential property, higher rate): £94,000 x 0.24 = £22,560

The tax is due by 60 days after completion for UK residential property, paid through a Capital Gains Tax on UK Property account (not through the usual self-assessment timeline).

Reducing Your Capital Gains Tax Liability

Several strategies can reduce CGT. Timing disposals to use the Annual Exempt Amount each year (selling assets across two tax years rather than one can use two exempt amounts). Using a Stocks and Shares ISA: gains within an ISA are completely free of CGT, so holding investments inside an ISA shelter is the most tax-efficient approach for most people. Transfer assets to a spouse or civil partner before sale: the transferred portion uses the recipient's exempt amount and may be taxed at a lower rate if they are a basic rate taxpayer. Bed and ISA: selling assets to crystallise gains within the Annual Exempt Amount and immediately repurchasing them inside an ISA. Offsetting capital losses against gains: losses from other disposals in the same year (or carried forward from previous years) reduce the taxable gain pound for pound. Claiming Business Asset Disposal Relief (formerly Entrepreneurs' Relief): qualifying business owners pay a reduced 10% rate on gains up to a lifetime limit of £1 million.

Frequently Asked Questions

Do I pay CGT on my main home? No. The sale of your only or main residence is fully exempt from CGT under Private Residence Relief (PRR). If you have used the property as your main home for the entire period of ownership, there is no CGT liability. If you let the property, had a period of non-occupation, or owned more than one property at the same time, partial relief may apply, and the calculation becomes more complex.

When do I need to report and pay CGT on property? For UK residential property, you must report and pay any CGT within 60 days of completion of the sale, using the HMRC Capital Gains Tax on UK Property service. For other assets, CGT is reported through self-assessment by the 31 January deadline following the end of the tax year in which the disposal occurred. Missing the 60-day deadline for property attracts an automatic penalty.

Can I carry forward capital losses? Yes. Unused capital losses from any previous tax year can be carried forward indefinitely and offset against future gains. Losses must first be used against gains in the same tax year (even if it means giving up the Annual Exempt Amount), and any remaining loss is then carried forward. Report losses to HMRC within 4 years of the tax year in which they arose.

Are shares in an ISA subject to CGT when I sell? No. All gains within a Stocks and Shares ISA are exempt from CGT, regardless of the size of the gain. This is one of the key tax advantages of the ISA wrapper. There is no ISA tax reporting requirement; ISA gains do not need to be included on a self-assessment return.

Worked example: shares sold by a basic rate taxpayer

The property example above sits entirely inside the higher rate, so it never reaches the split between the two CGT rates. A share disposal by someone with income below the higher rate threshold does.

Take an investor with a salary of 25,000. Shares bought for 12,000 are sold for 40,000, and the broker's dealing charges of 200 count as an allowable cost.

The two rates divide the taxable gain rather than applying one rate to all of it. The basic rate band for 2024/25 runs to 37,700 of taxable income. The salary of 25,000 uses 25,000 of it, leaving 12,700 unused.

The effective rate on the taxable gain is 5,190 divided by 24,800, which is 20.9 percent. On the full 27,800 gain it is 18.7 percent. Neither figure appears in the legislation, and both are useful only if you say what they are a percentage of.

The same 27,800 gain produces a different bill at each income level, because the size of the unused basic rate band changes.

The step between 20,000 and 25,000 of income is 300 of extra tax on an unchanged gain, and it arrives purely because 5,000 of the gain moved from the 18 percent slice to the 24 percent slice.

What the October 2024 rate change did to the same numbers

The rates that apply to assets other than residential property rose from 10 and 20 percent to 18 and 24 percent for disposals on or after 30 October 2024. Rates on residential property were already 18 and 24 percent and did not change.

The increase is larger for the lower-income investor, because more of the gain sat in the slice that moved from 10 to 18 percent. That is the opposite of what a headline reading of "rates went up by eight points and four points" would suggest.

Using two tax years

The Annual Exempt Amount is 3,000 per person per tax year and cannot be carried forward. Disposing in two tranches across a tax year boundary uses the allowance twice.

Splitting the 27,800 gain into two equal halves of 13,900 gives a taxable gain of 10,900 in each year. At 24 percent that is 2,616 a year, or 5,232 across the two years, against 5,952 in a single year. The saving is 720.

Two conditions apply before that saving means anything. The exemption is worth having only if the rate stays the same across the two years, so a change in rates can wipe it out. And a disposal that has economically happened cannot be dressed up as two disposals; the tranches have to be genuine transactions with real market risk between them.

Spouses and civil partners have a further tool. Assets can be transferred between them at no gain and no loss, so a gain can be moved to whichever of the two has more unused basic rate band before the sale. The transfer itself does not trigger a charge, and the recipient's own 3,000 exemption is then available.

What the calculator models, and what it leaves out

The calculator applies the rates and allowance in force for the 2024/25 tax year. It computes the gain as proceeds minus purchase cost minus allowable costs, then subtracts the Annual Exempt Amount, then splits the taxable gain between the two rates according to the unused basic rate band implied by the income figure you enter. Where the input asks for a band rather than a figure, the tool assumes an unused band large enough to hold the whole gain, or none of it, and the real answer for a borderline case lies between the two.

It does not model Private Residence Relief, which can remove all or part of a gain on a home that qualified as a main residence for part of the ownership period, including the final nine months of ownership. It does not apply Lettings Relief, which since April 2020 is available only where the owner shared occupancy with the tenant. It does not handle non-resident surcharges or the rebasing rules that apply to non-residents, trustees or personal representatives. It does not net off capital losses, and it does not apply Business Asset Disposal Relief, whose rate rose to 14 percent for disposals on or after 6 April 2025 and rises again to 18 percent for disposals on or after 6 April 2026.

It also does not deal with the interaction between gains and income that can move a taxpayer across the higher rate threshold, which is the most common reason a hand calculation disagrees with an HMRC computation. Gains stack on top of income for the purpose of finding the unused basic rate band, and a gain can itself be large enough to consume it.

Where the figures come from

The rates and the Annual Exempt Amount are set out in the Taxation of Chargeable Gains Act 1992. Sections 1H and 1I specify the rates, and Schedule 1B defines what counts as residential property for the higher rates. The Autumn Budget 2024 measure that raised the non-property rates to 18 and 24 percent is published by HM Revenue and Customs as "Capital Gains Tax: rates of tax", and confirms that the residential property rates of 18 and 24 percent were left unchanged from 6 April 2024. The income tax basic rate band of 37,700 and personal allowance of 12,570 used in the tables above are the 2024/25 figures from the same Budget's rates and allowances annex, and both were unchanged from 2021/22.

Also try these free tools:

• UK Income Tax Calculator
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• Investment Calculator