UK Capital Gains Tax Calculator

Capital gains tax (CGT) is the tax on the profit when you sell something for more than it cost you. For 2026/27 the rates are 18% and 24% for individuals, and they now apply across the board: residential property, shares and other assets have all shared the same two rates since 30 October 2024. Which rate you pay depends on your income. The gain is stacked on top of your taxable income, taxed at 18% while it sits inside your unused basic-rate band and 24% once it goes above.

The calculation of capital gains tax starts with the gain, not the sale price. Take your disposal proceeds, deduct the original purchase price, then deduct your allowable costs: for a property that is legal and agent fees, the SDLT you paid on the way in and the cost of capital improvements; for shares it is dealing costs and the stamp duty on the purchase. Everyone then has a capital gains tax allowance, the annual exempt amount, of £3,000 for 2026/27. Only the gain above that is taxed, which is exactly what this CGT calculator estimates.

Property and shares part company on reporting, not on rates. A UK resident selling residential property must report the disposal and pay the tax within 60 days of completion where tax is due, using HMRC's CGT on UK property account, separately from Self Assessment. A gain on shares goes on your Self Assessment return instead (or HMRC's real-time CGT service), with payment by the normal 31 January deadline.

Two things this capital gains tax estimator deliberately does not model. If the property was ever your main home, Private Residence Relief and final-period relief can reduce or remove the gain, and that depends on your occupation history. For shares, the matching rules (same-day and 30-day bed-and-breakfast rules) can change your base cost. Both are exactly the situations where advice pays for itself, and we can work out your precise position including any reliefs.