How much capital gains tax do I pay in the UK?

For disposals of shares, funds, and ETFs from 30 October 2024 onwards, basic rate taxpayers pay 18% and higher/additional rate taxpayers pay 24% on gains above the annual exempt amount. Before that date, the rates were 10% and 20% respectively. The annual exempt amount for 2024/25 is £3,000.

What is the capital gains tax allowance for 2024/25?

The annual exempt amount (tax-free allowance) for the 2024/25 tax year is £3,000. This is the same for 2025/26. It was reduced from £6,000 in 2023/24 and £12,300 in 2022/23.

How does the 30-day bed and breakfast rule work?

If you sell shares and repurchase shares of the same type within 30 days, the sale is matched with the subsequent purchase for CGT purposes. This anti-avoidance rule prevents investors from selling to realise a loss and immediately rebuying. FiscalFox applies this rule automatically.

Do I need to file SA108 for capital gains?

You need to complete the SA108 supplementary pages if your total disposal proceeds exceed 4 times the annual exempt amount (£12,000 for 2024/25), if you have chargeable gains above the annual exempt amount, or if you want to claim capital losses.

What is the best capital gains tax calculator for UK shares?

FiscalFox is a specialist UK capital gains tax calculator for share investors. It applies all three HMRC share matching rules automatically - same-day rule, 30-day bed and breakfast rule, and Section 104 pooling - and generates SA108-ready reports. It supports Vanguard, Hargreaves Lansdown, Freetrade, Trading 212, eToro, InvestEngine, Moneybox, Saxo Bank, and Interactive Brokers natively, plus any other broker via AI-powered CSV import.

How do I report share sales to HMRC?

Share sales are reported on the SA108 supplementary pages of your Self Assessment tax return. You need to calculate the gain or loss on each disposal using HMRC's share matching rules, then enter the totals on SA108. The deadline is 31 January following the end of the tax year. FiscalFox can generate the SA108 schedules automatically from your broker export files.

Do I need to pay capital gains tax if my gains are under GBP 3,000?

If your total capital gains for 2024/25 or 2025/26 are under the GBP 3,000 annual exempt amount, you do not owe CGT. However, you may still need to file SA108 if your total disposal proceeds exceed GBP 12,000 (4 times the exemption), or if you want to claim capital losses to carry forward.

How do I calculate capital gains on shares?

Capital gains on shares are calculated as disposal proceeds minus allowable costs (purchase price plus dealing fees). HMRC requires you to identify which shares are being sold using share matching rules: same-day rule first, then the 30-day bed and breakfast rule, then Section 104 pooling. FiscalFox automates this entire process.

What is the Section 104 pooling rule?

The Section 104 pool is a running average cost calculation for shares of the same type. When you buy shares, the cost is added to the pool. When you sell shares not matched by the same-day or 30-day rules, the cost is calculated as a proportion of the total pool cost based on the number of shares sold.

What are the current UK CGT rates?

From 30 October 2024: 18% for basic rate taxpayers and 24% for higher/additional rate taxpayers on shares and other assets. Before 30 October 2024: 10% and 20% respectively. Residential property has different rates.

What is the same-day rule for capital gains?

The same-day rule requires that if you sell shares and buy shares of the same type on the same day, the sale is matched with the same-day purchase for CGT purposes, regardless of the order of transactions during the day.

Can I carry forward capital losses?

Yes. If your capital losses exceed your capital gains in a tax year, you can carry forward the excess losses to offset against future capital gains indefinitely. You must report the losses to HMRC within 4 years of the end of the tax year in which they arose.

Is it really free to start?

Yes. Capital gains calculations are completely free. You can upload transaction files from up to 2 platforms, calculate your gains and losses, and view results at no cost. The premium tier (£29.99 per tax year) is only needed for exporting HMRC-ready reports and unlimited platform support.

Do you support my broker?

FiscalFox works with any broker. We have built-in support for Vanguard, Hargreaves Lansdown, Freetrade, Trading 212, eToro, InvestEngine, Moneybox, Saxo Bank, and Interactive Brokers with automatic format detection. For any other broker, our AI-powered parser automatically detects your CSV column layout and imports your transactions securely.

Is FiscalFox HMRC-compliant and secure?

Yes. FiscalFox applies all three HMRC share matching rules in the correct priority order. All data is encrypted using AES-256-GCM, transaction files are processed client-side in your browser, and no files are stored in our databases.

When did CGT rates change in the UK?

The most recent change was on 30 October 2024, when the Autumn Budget increased CGT rates on shares from 10%/20% to 18%/24%. The annual exempt amount was reduced from £12,300 to £6,000 in April 2023, and further reduced to £3,000 in April 2024.

How do I know FiscalFox's calculations are correct?

FiscalFox applies the exact same share-matching rules HMRC uses to verify Self Assessment returns: same-day matching, 30-day bed and breakfast rules, and Section 104 pooling, in the correct priority order. Every disposal is traced and the calculations are defensible if you are ever questioned.

When do I need to upgrade to Premium?

The free tier lets you calculate and view your capital gains on-screen. Upgrade to Premium (£29.99 per tax year, one-time payment) when you want to download HMRC-ready PDF and CSV reports for your Self Assessment.

Is there a subscription?

No. Premium is a one-time payment per tax year. Pay £29.99 once and download your reports as many times as you need for that tax year. There are no recurring charges or hidden fees.

Can I use FiscalFox with Claude Code or another AI agent?

Yes. The FiscalFox CLI is a standalone command-line tool designed for AI coding agents such as Claude Code, Cursor, GitHub Copilot, and Windsurf. You give the agent your broker file and it handles parsing, normalizing, and calculating your capital gains using HMRC share matching rules. No AI is involved in the tax calculation itself.

What is the FiscalFox CLI?

The FiscalFox CLI is a command-line version of the FiscalFox calculator. It uses the same HMRC-compliant engine as the web app. Install it with npm install -g fiscalfox or run with npx. It outputs structured JSON results including disposals, Section 104 pool balances, SA108 box values, and estimated tax liability.

Capital Gains Tax Rates 2024/25 - October 2024 Changes

Capital gains tax rates on shares and other non-property assets changed significantly during the 2024/25 tax year. As announced in the HM Treasury Autumn Budget 2024 policy paper "Capital Gains Tax rates for carried interest, and for other disposals by individuals," the Autumn Budget on 30 October 2024 increased the rates with immediate effect, creating a split-year scenario for the 2024/25 tax year. This guide explains the old and new rates, how the split-year calculation works, and how your income tax band affects the rate you pay.

Budget change

CGT rates on shares increased from 10%/20% to 18%/24% with immediate effect from 30 October 2024. This creates a split-year calculation for the 2024/25 tax year.

CGT rates before 30 October 2024

For disposals of shares and other non-property assets made on or before 29 October 2024, the following rates applied:

Tax band	Rate (shares and other assets)
Basic rate	10%
Higher / additional rate	20%

These rates had been in place since 2016 and were among the lowest CGT rates in the OECD.

CGT rates from 30 October 2024

For disposals made on or after 30 October 2024, the new rates are:

Tax band	Rate (shares and other assets)
Basic rate	18%
Higher / additional rate	24%

The increase took effect immediately from 30 October 2024 - the date of the Autumn Budget announcement, amending the CGT rate provisions in TCGA 1992. The rates for 2025/26 remain at 18% and 24%.

The split-year calculation for 2024/25

Because the rate change took effect partway through the 2024/25 tax year (which runs from 6 April 2024 to 5 April 2025), you may have disposals at both the old and new rates. GOV.UK capital gains rates guidance and the SA108 Notes for 2024/25 require you to apply the rate that was in force on the date of each disposal:

Disposals between 6 April 2024 and 29 October 2024: 10% (basic rate) or 20% (higher rate).
Disposals between 30 October 2024 and 5 April 2025: 18% (basic rate) or 24% (higher rate).

However, the annual exempt amount of £3,000, any capital losses, and the basic-rate band calculation apply to the year as a whole - they are not split. You first calculate your net chargeable gains for the full year, then apportion the taxable amount between the pre- and post-Budget periods to apply the correct rates.

Worked example - split-year

Tom is a higher-rate taxpayer. During 2024/25, he makes the following disposals:

15 July 2024: sells shares for a gain of £4,000 (pre-Budget - 20% rate applies).
20 November 2024: sells shares for a gain of £6,000 (post-Budget - 24% rate applies).

Total gains: £10,000. After deducting the £3,000 annual exempt amount, Tom has £7,000 of taxable gains.

The £3,000 AEA is apportioned proportionally against the gains, then the appropriate rate is applied to each portion. In practice, HMRC allows you to allocate the AEA in the most beneficial way. Here, Tom would allocate as much AEA as possible against the higher-rate gains:

Pre-Budget taxable gain: £4,000 - £1,200 AEA = £2,800 at 20% = £560
Post-Budget taxable gain: £6,000 - £1,800 AEA = £4,200 at 24% = £1,008
Total CGT: £1,568

How your income tax band affects your CGT rate

The CGT rate you pay depends on your total taxable income. The basic-rate band for income tax in 2024/25 is £37,700 (on top of the £12,570 personal allowance, meaning income up to £50,270 is taxed at the basic rate).

When calculating CGT, your capital gains sit on top of your income. If your taxable income is below £50,270, you have unused basic-rate band available for your gains:

Gains that fall within the remaining basic-rate band are taxed at the basic rate (10% pre-Budget, 18% post-Budget).
Gains that exceed the remaining basic-rate band are taxed at the higher rate (20% pre-Budget, 24% post-Budget).

Worked example - mixed rate bands

Emma has a salary of £45,000 in 2024/25. Her taxable income after the personal allowance is £32,430. She has £5,270 of unused basic-rate band (£37,700 - £32,430). On 15 December 2024 (post-Budget), she sells shares for a gain of £10,000. After the £3,000 AEA, she has £7,000 of taxable gains.

First £5,270 taxed at 18% (basic rate): £5,270 x 18% = £948.60
Remaining £1,730 taxed at 24% (higher rate): £1,730 x 24% = £415.20
Total CGT: £1,363.80

Residential property rates

Residential property that is not your main home has always attracted higher CGT rates. Before 30 October 2024, the rates were 18% (basic) and 28% (higher). From 30 October 2024, the rates are 18% (basic) and 24% (higher) - meaning the higher-rate property surcharge has actually been reduced. This guide focuses on shares, but it is worth noting that property rates have now converged with the new share rates at the higher-rate level.

Business Asset Disposal Relief (BADR)

Business Asset Disposal Relief (formerly Entrepreneurs' Relief), governed by TCGA 1992 s.169H-169S, allows qualifying business owners to pay a reduced rate of CGT on the disposal of business assets. The rate remains at 10% for 2024/25 on gains up to a lifetime limit of £1 million. However, as confirmed in the Autumn Budget 2024 policy paper, this is set to increase to 14% from 6 April 2025 and to 18% from 6 April 2026. This relief does not apply to ordinary share disposals by investors - it is only available for qualifying business disposals.

Investors' Relief

Investors' Relief provides a 10% CGT rate on qualifying shares in unlisted trading companies, up to a lifetime limit of £10 million. The qualifying conditions are strict: shares must have been held for at least three years, and the investor must not be an employee or officer of the company (with limited exceptions). Like BADR, the rate is set to increase to 14% from April 2025 and 18% from April 2026.

Summary of rates

Asset type	Basic rate (pre-30 Oct)	Higher rate (pre-30 Oct)	Basic rate (post-30 Oct)	Higher rate (post-30 Oct)
Shares and other assets	10%	20%	18%	24%
Residential property	18%	28%	18%	24%
BADR / Investors' Relief	10%	10%	10%	10%

How FiscalFox handles the rate change

FiscalFox automatically applies the correct CGT rate based on the date of each disposal. For the 2024/25 tax year, it identifies whether each sale occurred before or after 30 October 2024 and calculates the tax accordingly. The generated report clearly shows which rate was applied to each disposal.