UK Capital Gains Tax calculator
Work out UK Capital Gains Tax on gains from shares, property and other assets using dated GOV.UK and HMRC rates and the tax-free allowance for 2026/27 and 2025/26.
A clear answer. Here’s how.
The tax-free allowance (£3,000 for individuals in 2026/27) is set against the gains charged at the highest rates. Your basic rate band (£37,700) less your taxable income is what is left for gains: gains qualifying for Business Asset Disposal Relief use it first, then other gains are charged at 18% within what is left and 24% above it. Relief gains are charged at 18% in 2026/27. Rates and the allowance come from the dataset for the tax year you choose, which covers the date of the sale, and the calculator refuses to run if no dataset covers today’s date.
What this does not include
- Working out the gain itself: what you paid, fees and improvement costs, market value rules, the main-home exemption, reliefs other than Business Asset Disposal Relief, and exempt assets. Enter the gains after allowable losses.
- Losses. Deduct the allowable losses you are using before you enter gains: current-year losses come off in full, and GOV.UK says unused losses from earlier years come off only down to the tax-free allowance.
- Trustees, personal representatives, companies and non-residents. Trustees and personal representatives pay 24% and trustees have a lower allowance; none of that is modelled.
- Carried interest (a higher CGT rate in 2025/26 and Income Tax and National Insurance from 6 April 2026), Investors’ Relief and the foreign income and gains regime, under which no tax-free allowance is available.
- The Business Asset Disposal Relief lifetime limit. The tool stops at £1,000,000 of relief gains and does not know what you have claimed before.
- Scottish taxpayers. The basic rate band used is the £37,700 that HMRC publishes for England, Wales and Northern Ireland; the tool has not checked a different band for Scotland.
- Reporting and paying: UK residential property sales are reported and paid within 60 days of completion, and gains over the reporting thresholds go on a Self Assessment return. Interest and penalties are not included.
- Gift Aid and relief-at-source pension contributions, which extend the basic rate band, and Income Tax on the same income.
How this is checked
4 reference checks passed These 4 cases were run when this page was built, on 20 October 2026, and all reproduce within the stated tolerance. The same cases are part of the automated tests that run on every change to Toolmoz. Engine version 1.
See the checks and where each expected answer comes from
Case 1
- Inputs
- Tax year 2026-27Your taxable income (£) 20000Gains that do not qualify for relief (£) 12600Gains qualifying for Business Asset Disposal Relief (£) 0
- Expected, and what Toolmoz gave
- Capital Gains Tax expected 1728, Toolmoz 1728
- Where the expected answer comes from
- GOV.UK: Capital Gains Tax rates (examples 1 and 2, 2026/27)
- Allowed difference
- ±0.005
Case 2
- Inputs
- Tax year 2026-27Your taxable income (£) 20000Gains that do not qualify for relief (£) 52600Gains qualifying for Business Asset Disposal Relief (£) 0
- Expected, and what Toolmoz gave
- Capital Gains Tax expected 10842, Toolmoz 10842
- Where the expected answer comes from
- GOV.UK: Capital Gains Tax rates (examples 1 and 2, 2026/27)
- Allowed difference
- ±0.005
Case 3
- Inputs
- Tax year 2026-27Your taxable income (£) 60000Gains that do not qualify for relief (£) 10000Gains qualifying for Business Asset Disposal Relief (£) 0
- Expected, and what Toolmoz gave
- Capital Gains Tax expected 1680, Toolmoz 1680
- Where the expected answer comes from
- HMRC: Capital Gains Tax rates and allowances (2025/26 rates and allowance)
- Allowed difference
- ±0.005
Case 4
- Inputs
- Tax year 2025-26Your taxable income (£) 30000Gains that do not qualify for relief (£) 20000Gains qualifying for Business Asset Disposal Relief (£) 50000
- Expected, and what Toolmoz gave
- Capital Gains Tax expected 11080, Toolmoz 11080
- Where the expected answer comes from
- GOV.UK: Business Asset Disposal Relief (order in which the basic rate band is used)
- Allowed difference
- ±0.005
What this shows: the engine reproduces independently worked values for these cases. It does not prove every possible input is right. To test an answer you were given, see how to check a number; to see what is and is not checked across Toolmoz, see the accuracy ledger.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Tax year
- 2026/27 (6 April 2026 to 5 April 2027)
- Your taxable income (£)
- 20000
- Gains that do not qualify for relief (£)
- 12600
- Gains qualifying for Business Asset Disposal Relief (£)
- 0
Example result
| Gains | Gains (£) | Tax-free allowance used (£) | Taxable gains (£) | Rate | Tax (£) |
|---|---|---|---|---|---|
| Other gains within the basic rate band | 12,600 | 3,000 | 9,600 | 18% | 1,728 |
| Total | 12,600 | 3,000 | 9,600 | 1,728 |
Valid for United Kingdom tax year 2026/27 (6 April 2026 to 5 April 2027). Source: official GOV.UK and HMRC pages, linked below. Reviewed on 18 October 2026. These are the rules in force today. Basic rate band left after your taxable income: £17,700.00. The tax-free allowance (£3,000) is used against the gains charged at the highest rates first. Estimate only, not tax, legal or financial advice: see what is not included below.