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.

InvestEngine Capital Gains Tax Calculator

InvestEngine is a UK investment platform specialising in commission-free ETF investing. The platform offers both a DIY portfolio option, where you choose your own ETFs, and a managed portfolio option, where InvestEngine builds and rebalances a portfolio for you. If you hold ETFs in an InvestEngine Personal Account (their general investment account, as opposed to their ISA), any gains from selling those holdings may be subject to UK capital gains tax. FiscalFox reads your InvestEngine trading statement and automatically applies HMRC's share matching rules to calculate your CGT liability.

How to download your InvestEngine trading statement

InvestEngine provides your transaction data as a downloadable CSV file. Follow these steps to obtain it:

Log in to your InvestEngine account at investengine.com.
Navigate to Statements from your account menu or dashboard.
Select Trading Statement from the available statement types.
Choose the date range that covers the period you need. For the most accurate CGT calculation, select a range starting from your first ever trade through to the end of the tax year you are filing for. This allows FiscalFox to build a complete Section 104 pool history for each ETF.
Click Download CSV to export the trading statement.
Save the .csv file to your computer.

Auto-rebalancing creates taxable events

If you use InvestEngine's managed portfolio or auto-rebalance features, each rebalancing trade is a disposal for CGT purposes. These appear as regular Buy and Sell transactions in your statement and FiscalFox processes them all automatically.

With the CSV ready, go to your FiscalFox dashboard, select InvestEngine as your broker, and upload the file to start your calculation.

File format details

InvestEngine exports your trading statement as a CSV (comma-separated values) file. The file typically includes the following columns:

Date -- the date the transaction was executed
Account -- the account type (Personal Account or ISA)
Type -- the transaction type, such as Buy, Sell, or Dividend
Instrument -- the name or ticker of the ETF
ISIN -- the International Securities Identification Number
Quantity -- the number of units traded
Price -- the execution price per unit
Amount -- the total transaction value in GBP
Notes -- additional context, such as whether the trade was part of an auto-rebalance

FiscalFox reads this file entirely in your browser. Your InvestEngine data is never uploaded to or stored on our servers.

How FiscalFox processes your InvestEngine data

When you upload your InvestEngine CSV, FiscalFox first separates transactions by account type, keeping only Personal Account (GIA) transactions for CGT purposes. It then applies HMRC's share matching rules in the legally required priority order:

Same-day rule -- ETF units sold on the same day they were purchased are matched first, with the gain or loss calculated using the actual purchase cost from that day.
30-day bed and breakfast rule -- if you sold ETF units and repurchased the same ETF within 30 days, the disposal is matched against the repurchase. This includes auto-rebalancing trades that may trigger a sell and subsequent buy of the same instrument.
Section 104 pool -- all remaining disposals are matched against the pooled average cost for each ETF, which FiscalFox maintains as a running calculation updated with every transaction.

The output report provides a disposal-by-disposal breakdown showing the matching rule applied, the cost basis, proceeds, and resulting gain or loss. The summary section gives you the figures needed for your Self Assessment tax return, including total disposals, total gains, total losses, and the net chargeable gain after the annual exempt amount.

Common issues with InvestEngine files

Auto-rebalancing trades

If you use InvestEngine's managed portfolio or auto-rebalance features, the platform periodically sells and buys ETFs to maintain your target asset allocation. These rebalancing trades appear in your trading statement as regular Buy and Sell transactions. FiscalFox processes them the same way as manual trades, because each sale is a disposal for CGT purposes regardless of whether you initiated it manually or it was triggered by auto-rebalancing. This can result in more disposals than you might expect, but each one is correctly calculated.

Only GIA transactions are relevant for CGT

InvestEngine offers both a Personal Account (GIA) and an ISA. Only transactions in the Personal Account are subject to capital gains tax. The trading statement CSV may include transactions from both accounts. FiscalFox identifies transactions by account type and processes only the Personal Account data for CGT calculations. You do not need to manually filter the file.

Small rebalancing amounts

Auto-rebalancing may generate trades with very small values (sometimes just a few pounds). While individually insignificant, these are still taxable events and must be included in your CGT calculation for completeness. FiscalFox processes all trades regardless of size, ensuring your report is fully accurate and HMRC-compliant.

Supported transaction types

FiscalFox extracts and processes the following transaction types from your InvestEngine trading statement:

Transaction Type	How FiscalFox Uses It
Buy	Added to the Section 104 pool for the relevant ETF
Sell	Matched against acquisitions using HMRC share matching rules
Dividend	Recorded for reference (taxed under income tax, not CGT)
Auto-rebalance Buy	Treated as a standard buy and added to the Section 104 pool
Auto-rebalance Sell	Treated as a standard disposal and matched using HMRC rules

InvestEngine's focus on ETFs and its clean CSV format make it well-suited for automated CGT calculations. If you have questions about how FiscalFox handles specific InvestEngine transactions, or if you encounter issues with your trading statement, visit our support page for help.