Capital Gains Tax on Shares Calculator UK 2026/27

Explore More Capital Gains Tax Calculators

Shares & Funds CGT Basics

Gains on shares, funds and other investments held outside an ISA or pension are subject to the same CGT rates as other assets: 18% within your remaining basic rate band, 24% above it, after the £3,000 annual exempt amount.

Multiple trades of the same holding

If you bought and sold the same share on different dates at different prices, your actual taxable gain depends on HMRC's share identification rules, applied in this order:

Rule	What it does
Same-day rule	Shares bought and sold on the same day are matched first
30-day rule ("bed and breakfast")	Shares sold, then rebought within 30 days, are matched to the rebuy
Section 104 pool	Remaining shares of the same type are pooled and averaged

This calculator deliberately doesn't attempt that matching — it's built for a simple "I sold once, what do I owe" estimate. Multi-trade portfolios need a dedicated tool or an accountant.

How this calculator works — Formulas & Method

Source: gov.uk/capital-gains-tax/rates · Deterministic calculation — no AI, no arbitrary estimation

Constants used

Constant	Value	Source
Annual exempt amount	£3,000	gov.uk/capital-gains-tax/rates, 2026/27
Basic rate band upper limit	£50,270 taxable income	gov.uk Income Tax rates 2026/27
CGT basic / higher rate	18% / 24%	gov.uk/capital-gains-tax/rates

Formulas

      
      — Taxable gain —

      taxable_gain = max(0, gain − £3,000)

      — Rate band —

      basic_band_remaining = max(0, £50,270 − other_taxable_income)

      at_18pct = min(taxable_gain, basic_band_remaining)

      at_24pct = taxable_gain − at_18pct

      cgt = at_18pct × 18% + at_24pct × 24%

Deterministic calculation for a single disposal. Doesn't apply HMRC's same-day/30-day/Section 104 share-matching rules for multiple trades of the same holding; always confirm your own position with HMRC or a qualified adviser.

Shelter Future Gains From CGT Entirely

The calculation above is for a gain you've already made. For future gains, the standard mitigation is simple: hold investments inside a Stocks & Shares ISA, where gains are never subject to Capital Gains Tax.

Sold shares outside a wrapper: consider a "Bed and ISA" — sell and immediately repurchase the same holding inside an ISA, using this year's £20,000 ISA allowance.
Building a portfolio from scratch: route new investments through an ISA or SIPP first, before a general investment account.
Approaching the £3,000 CGT allowance each year: moving holdings into an ISA gradually, using each year's allowance, avoids a large taxable disposal later.

Investment platforms like Hargreaves Lansdown, interactive investor and Trading 212 make ISA transfers and Bed-and-ISA straightforward.

Compare Investment Platforms →

Transparency & Methodology

Shares Capital Gains Tax Calculator

Independent, Open-Source Estimator

An independent calculator applying published HMRC CGT rates deterministically — no AI estimate, no official affiliation.

Methodology & Sources

Figures are public HMRC rates. For your exact position, use gov.uk/capital-gains-tax.

Not Tax or Legal Advice

Information only. Consult the Chartered Institute of Taxation or an adviser via the FCA Register.

Open Source

Formulas are public. Inspect on GitHub.

Frequently Asked Questions

How is Capital Gains Tax on shares calculated?

Your gain (sale proceeds minus purchase cost and dealing fees) has the £3,000 annual exempt amount deducted, then the remainder is taxed at 18% within your remaining basic rate band and 24% above it — the same rates as other chargeable assets.

Does this calculator handle multiple share trades?

No — it's scoped to a single disposal estimate. If you bought and sold the same share multiple times at different prices, HMRC's same-day, 30-day and Section 104 pooling rules apply, which this simple tool doesn't model. Use a dedicated multi-trade matching tool or an accountant for that.

How do I avoid CGT on shares?

Holding shares inside a Stocks & Shares ISA or pension shelters gains from CGT entirely. "Bed and ISA" — selling and immediately repurchasing inside an ISA — is the standard way to move existing holdings into that shelter using your annual ISA allowance.

What is the CGT allowance for shares in 2026/27?

The same £3,000 annual exempt amount applies across all asset types, not just shares — it's a single allowance per person per tax year, shared across property, shares, crypto and other gains.