CGT on Shares Calculator

Calculate capital gains tax on share sales. Includes annual exempt amount, basic/higher rates and ISA tip.

Last updated: April 2026 · Source: GOV.UK — Tax when you sell shares

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Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

Capital Gains Tax on shares uses the share-pooling method to calculate your cost basis. Under section 104 of TCGA 1992, all shares of the same class in the same company are pooled together with a single average cost per share. When you sell shares, the gain is the sale proceeds minus the pooled average cost multiplied by the number of shares sold.

Two exceptions override the pooling method. The same-day rule matches any shares sold with shares of the same type bought on the same day. The 30-day (bed and breakfasting) rule matches disposals with acquisitions within the following 30 days. These rules prevent artificial loss creation by selling and immediately repurchasing shares.

After applying the £3,000 annual exempt amount, basic-rate taxpayers pay 10% on gains and higher or additional-rate taxpayers pay 20%. If your gains plus income exceed the basic-rate threshold, the excess gains are taxed at the higher rate. Allowable costs include broker commissions and stamp duty on purchase.

Example: Selling 500 shares with pooled cost of £10 each

  1. Pooled cost: 500 × £10 = £5,000
  2. Sale proceeds: 500 × £18 = £9,000
  3. Gain: £9,000 − £5,000 = £4,000
  4. Less annual exempt amount: −£3,000
  5. Taxable gain: £1,000 at 20% (higher rate) = £200

Source: GOV.UK — Tax when you sell shares

Frequently Asked Questions

What does the CGT on Shares Calculator do?
Calculate capital gains tax on share sales. Includes annual exempt amount, basic/higher rates and ISA tip. All calculations are performed in your browser using official UK rates and thresholds.
Is this calculator suitable for financial decisions?
This calculator provides estimates for guidance only. Investment returns are not guaranteed and your capital is at risk. Consider seeking independent financial advice before making investment decisions.
Are ISA contributions tax-free?
Yes. The annual ISA allowance for 2025/26 is £20,000. Any interest, dividends or capital gains within an ISA are completely tax-free.