Quick answer
Our calculators follow the order HMRC uses: work out the gain, apply reliefs, deduct losses and the annual allowance, then tax the remainder at 18% or 24% for 2026/27. All rates and limits come from one table of official figures that every calculator and guide shares. Results are estimates and are shown to the nearest pound unless stated.
Key facts
- One table of official figures drives every calculator and every worked example.
- Order of calculation: gain, reliefs, losses, annual allowance, rate.
- Shares and crypto use the same-day, 30-day and Section 104 pool rules.
- Nothing you enter is sent to us. Calculations run in your browser.
- Calculators are estimates and do not replace a tax return or advice.
The figures we use
Every rate, allowance and limit used on this site is held in a single table in the calculation engine. The calculators read it, and the guides pull their numbers from it when the pages are built. This means a figure cannot be changed in one place and missed in another. The table below shows the main figures for the 2026/27 tax year, which runs from 6 April to 5 April.
| Item | Figure used |
|---|---|
| Annual exempt amount (individuals) | £3,000 |
| Annual exempt amount (most trustees) | £1,500 |
| Lower Capital Gains Tax rate | 18% |
| Higher Capital Gains Tax rate | 24% |
| Trustees and personal representatives | 24% |
| Business Asset Disposal Relief rate | 18% on up to £1,000,000 of lifetime gains |
| Personal allowance | £12,570 |
| Basic rate band | £37,700 |
| Chattels exemption | £6,000 |
| UK property reporting deadline | 60 days from completion |
| Self Assessment reporting trigger | Proceeds over £50,000 |
Where a rate or rule depends on the tax year, the page says which year it applies to. We show a tax-year label only where the rate depends on it. We do not put publication or update dates on pages, because a date on a page can make a correct rule look out of date.
The order of calculation
Our calculators follow this order for an individual.
- Proceeds. The sale price, or the market value for a gift or an inheritance.
- Cost. What you paid, plus allowable buying costs and improvements. Mortgage interest is never deducted.
- Selling costs. Agent, legal and other costs of selling.
- Gain. Proceeds less cost less costs.
- Reliefs. Private Residence Relief, Business Asset Disposal Relief and similar reliefs, where selected.
- Losses and the allowance. Losses from the same year, then the annual allowance, then losses brought forward down to the allowance.
- Rate. The taxable gain is placed on top of taxable income. The part inside the basic rate band is taxed at 18% and the part above it at 24%.
For trustees and personal representatives, the 24% rate applies to the whole gain, and the allowance used is the one that applies to that kind of taxpayer.
Shares and crypto
For shares, funds and crypto assets, the calculators apply HMRC’s matching rules in order. A disposal is matched first with acquisitions on the same day, then with acquisitions in the 30 days after it, and then with the Section 104 pool, which holds the average cost of everything else. Crypto assets are treated token by token with the same engine. Our Section 104 calculator shows each match.
What the calculators assume
To keep the tools usable, we make some assumptions, and we say so on each page.
- You are a UK resident for the whole tax year, unless the page says it covers non-residents.
- Your income is the amount you enter. We apply the personal allowance and the basic rate band to that income.
- The asset is held in your own name, unless you choose a share or a type of taxpayer.
- Amounts are in pounds sterling.
- Rounding happens at the end, so small differences from your return are possible.
What the calculators do not cover
The tools do not cover every situation. They do not model complex trusts, partnerships, foreign assets, remittance basis claims, offshore settlements, employee share schemes, or the detail of every relief. They cannot see facts that affect your tax, such as whether a property qualified as your main home for each period. For these cases, use the calculator for a first estimate and then check with HMRC or a qualified adviser.
How we test the engine
Every calculator is built on the same engine, and the engine has an automated test suite that runs through typical and awkward cases: gains that fall exactly on the allowance, losses larger than gains, gains that straddle the basic rate band, share disposals that match on the same day, and so on. Worked examples on the guides are generated by the engine, so the example text and the calculators agree.
Sources
Our primary sources are GOV.UK and HMRC guidance and UK legislation. Each guide ends with a list of the official pages it relies on, so you can check what we say. If official guidance and our page disagree, trust the official guidance and please tell us.
Corrections and changes
When a rate or a rule changes, we change the one table of figures and rebuild the pages. If we find an error, we correct it. We do not hide corrections. If you think a result is wrong, contact us with the figures you entered, and we will check it.
You can read more about who we are on our about page, and about the limits of our content in our disclaimer.