UK Capital Gains Tax Calculator

How to work out a capital gain

A capital gain is the sale price minus what you paid, minus allowable costs such as broker or estate agent fees, legal costs, stamp duty paid on purchase and improvement work. Gifts and sales to connected people below value use market value instead of the price.

Your gains for the tax year are added together, losses from the same year are deducted, then the £3,000 annual exempt amount. What is left is taxed at 18% to the extent it fits in your unused basic rate band and 24% above. Since 30 October 2024 the same rates apply to residential property, shares and most other assets.

Worked examples

Gain of £20,000 with taxable income of £35,000: after the £3,000 allowance, £17,000 is taxable. £15,270 fits in the remaining basic band at 18% and the rest is at 24%, a bill of £3,164.

Gain of £50,000 for a higher-rate taxpayer earning £60,000: £47,000 taxable, all at 24%, so £11,280.

A business owner selling a qualifying trading company with a £200,000 gain and claiming Business Asset Disposal Relief pays 18% on £197,000: £35,460. The relief applies to lifetime gains of up to £1,000,000.

Reporting deadlines

• UK residential property: report and pay within 60 days of completion using a Capital Gains Tax on UK property account, unless the gain is covered by reliefs and the allowance. If you file Self Assessment you also include it on your return.
• Other assets: report on your Self Assessment return by 31 January after the tax year, or use HMRC’s real-time service if you do not file a return.
• If you file Self Assessment, report disposals when total sale proceeds exceed £50,000 in the year, even if your gains are below the allowance.
• Losses must be claimed within 4 years of the end of the tax year of disposal to be carried forward.

Rules that change the answer

Transfers between spouses or civil partners living together are made at no gain, no loss. The receiving partner takes over the original cost, which lets couples use two annual exempt amounts and two basic rate bands when they sell.

Shares in the same company are pooled at average cost. If you buy back the same shares within 30 days of selling, special matching rules apply instead of the average, so “bed and breakfasting” does not crystallise a loss or gain.

You cannot use a loss on a disposal to a family member or other connected person except against a gain from the same person. Assets that become worthless can be claimed as a loss through a negligible value claim.

• Exempt: your main home (usually), your car, ISAs, UK gilts and Premium Bonds, and betting or lottery winnings.
• Personal possessions are exempt below £6,000.
• Carried interest is taxed as income from 6 April 2026, not as a capital gain.

Worked example: selling a buy-to-let

A landlord bought a flat for £200,000, paying £7,000 in stamp duty and legal fees, and sells it for £300,000 with £4,500 of agent and legal fees. The gain is £88,500.

After the £3,000 annual exempt amount, £85,500 is taxable. With other taxable income of £40,000, £10,270 is taxed at 18% and the rest at 24%, a bill of £19,904. This must be reported and paid within 60 days of completion, using an estimate of your income for the year if needed.

Mortgage repayments, interest and routine repairs already claimed against rental income cannot be deducted from the gain. Capital improvements such as an extension can be, if they still exist at the time of sale.

Business Asset Disposal Relief conditions

BADR reduces the rate to 18% on up to £1,000,000 of lifetime gains. For a sole trader or partner, you must have owned the business for at least 2 years up to the date you sell. For company shares, the company must have been your “personal company” for at least 2 years: you hold at least 5% of the shares and voting rights and are an employee or office holder.