Question 1

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

Accepted Answer

For disposals of shares, funds, and ETFs in 2026/27, taxable gains are generally charged at 18% to the extent they fall within the unused basic-rate band and 24% above it. The individual annual exempt amount is £3,000.

Question 2

What is the capital gains tax allowance for 2026/27?

Accepted Answer

The individual annual exempt amount for the 2026/27 tax year is £3,000. It was £6,000 in 2023/24 and £12,300 in 2022/23.

Question 3

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

Accepted Answer

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.

Question 4

Do I need to file SA108 for capital gains?

Accepted Answer

If you are registered for Self Assessment, you generally need to report gains when taxable gains exceed the annual exempt amount, when total disposal proceeds exceed £50,000 for 2023/24 onwards, or when you need to claim allowable losses or make another capital gains claim.

Question 5

What does FiscalFox calculate for UK shares?

Accepted Answer

FiscalFox is a specialist UK capital gains tax calculator for share investors. It applies same-day matching, the 30-day bed and breakfast rule, and Section 104 pooling, then generates SA108-ready supporting reports. It has 13 built-in imports: Vanguard, Hargreaves Lansdown, Freetrade, Trading 212, eToro, InvestEngine, Moneybox, Saxo Bank, Interactive Brokers, Robinhood, Revolut, AJ Bell, and IG.

Question 6

How do I report share sales to HMRC?

Accepted Answer

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.

Question 7

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

Accepted Answer

If your total taxable gains are under the annual exempt amount, you do not owe CGT on those gains. If you are registered for Self Assessment, you may still need to report when total disposal proceeds exceed GBP 50,000 for 2023/24 onwards, or to claim allowable losses.

Question 8

How do I calculate capital gains on shares?

Accepted Answer

Capital gains on shares are calculated as disposal proceeds minus allowable costs. HMRC requires same-day matching first, then acquisitions in the following 30 days, then Section 104 pooling. FiscalFox automates imported transaction matching and the current-year estimate. A brought-forward capital-loss balance must currently be applied separately.

Question 9

What is the Section 104 pooling rule?

Accepted Answer

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.

Question 10

What are the current UK CGT rates?

Accepted Answer

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.

Question 11

What is the same-day rule for capital gains?

Accepted Answer

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.

Question 12

Can I carry forward capital losses?

Accepted Answer

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.

Question 13

Is it really free to start?

Accepted Answer

Yes. Capital gains calculations are completely free, including calculations across multiple broker files. The one-time £29.99 payment is only needed to download the HMRC report pack, and unlocks the selected tax year plus earlier years in the calculation. There is no subscription.

Question 14

Do you support my broker?

Accepted Answer

FiscalFox has 13 built-in broker imports: Vanguard, Hargreaves Lansdown, Freetrade, Trading 212, eToro, InvestEngine, Moneybox, Saxo Bank, Interactive Brokers, Robinhood, Revolut, AJ Bell, and IG. Other supported transaction files can use the opt-in AI import path after sign-in and consent.

Question 15

Does FiscalFox apply HMRC share matching rules and protect data?

Accepted Answer

FiscalFox applies same-day, following-30-day and Section 104 matching in HMRC's prescribed order. Built-in broker parsing runs in the browser where possible; signed-in storage and opt-in AI parsing are described in the privacy policy. FiscalFox is a calculation tool, not tax advice or an HMRC submission.

Question 16

When did CGT rates change in the UK?

Accepted Answer

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.

Question 17

How do I know FiscalFox's calculations are correct?

Accepted Answer

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.

Question 18

When do I need to pay for the report pack?

Accepted Answer

The free tier lets you calculate and view your capital gains on-screen. Pay £29.99 only when you want the downloadable HMRC-ready PDF and CSV report pack. The payment unlocks the selected tax year and every earlier year contained in the calculation.

Question 19

Is there a subscription?

Accepted Answer

No. The report pack is a one-time £29.99 payment with no recurring charge. You can download the unlocked reports again whenever you need them.

Question 20

What happens if my capital gains are wrong on my tax return?

Accepted Answer

If HMRC finds an error in your Self Assessment, you pay the extra tax plus interest, and a careless mistake can carry a penalty of up to 30% of the underpaid tax. Most DIY errors come from missing the same-day and 30-day matching rules. FiscalFox applies them automatically and keeps the workings behind every disposal so you can evidence your figures.

UK Capital Gains Tax Calculator for Shares

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Calculate share gains using HMRC matching rules

1. Import

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3. Report

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Important limits

How the result can be checked

Frequently asked questions

What are the UK Capital Gains Tax rates for shares in 2026/27?

Which share matching rules does this calculator use?

Can FiscalFox import more than one broker?

Does the calculator apply losses brought forward from earlier tax years?