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UK Capital Gains Tax Calculator (2025-26 & 2026-27)
You’ve sold — or you’re about to — and the CGT rules have changed again.
Computes UK Capital Gains Tax on a disposal using the current rules: the £3,000 annual exempt amount, the 18%/24% rates that have applied to ALL assets since 30 October 2024, the income-stacking rule that decides how much of the gain falls at 18% vs 24%, and Business Asset Disposal Relief with its stepping rate (14% in 2025-26, 18% from 6 April 2026) and £1 million lifetime limit. General AI reliably gets this wrong three ways at once — quoting the abolished £12,300 allowance, the dead 10%/20% share rates, and a BADR rate from the wrong year — and answers without asking for your taxable income, the input that actually sets the rate.
基準： Rates from 30 Oct 2024 (18%/24% all assets) · AEA £3,000 · BADR 14% (2025-26) → 18% (from 6 Apr 2026) · £1M lifetime limit · gov.uk, verified 2026-07-23
数値
- Capital Gains Tax due
- £3,918
- on a £20,000 gain, 2026-27
- Effective rate on the whole gain
- 19.59%
- tax ÷ gross gain
- Taxable gain after allowance
- £17,000
- £3,000 annual exempt amount deducted
- Taxed at 18% (basic band)
- £2,700
- tax £486
- Taxed at 24% (above the band)
- £14,300
- tax £3,432
実務者の読み解き
知っておきたい点
£2,700 of your gain fell in your unused basic-rate band at 18%; £14,300 above it at 24%. £2,700 more income this year would have pushed the whole gain to 24% — the rate on your gain is set by your income, which is why "what’s CGT on £20,000" has no answer without it.
知っておきたい点
The annual exempt amount was £12,300 as recently as 2022-23; it is now £3,000. At that level nearly every real disposal is taxable — if a source (or an AI) told you a £12,300 or £6,000 allowance, it is quoting a dead number.
知っておきたい点
Transfers between spouses or civil partners are no-gain-no-loss: giving part of an asset to your spouse before selling means two £3,000 allowances and two basic-rate bands can apply. Standard planning — but the transfer must be genuine and outright.
知っておきたい点
This is a calculation on the figures you entered, not tax advice. Losses, EIS/SEIS reliefs, gift holdover, non-residence, and trust situations all change the answer — for anything beyond a straightforward disposal, check with HMRC guidance or an adviser.
計算方法
Rates: since 30 October 2024 the main CGT rates are 18% (within your unused basic-rate band) and 24% (above it) for ALL assets — the old 10%/20% rates for shares and other non-property assets are gone, and residential property no longer has separate higher rates (its old 18%/28% converged to the same 18%/24%). Both the 2025-26 and 2026-27 tax years use these rates.
Annual exempt amount: £3,000 in both years, deducted from the gain first (skipped here if you say other gains already used it). It was £12,300 in 2022-23 and £6,000 in 2023-24 — the source of most stale answers.
Band mechanics (gov.uk method): the taxable gain (after the allowance) stacks on top of your taxable income (income after the personal allowance). The slice that fits in the unused basic-rate band — max(0, £37,700 − taxable income), capped at the taxable gain — is taxed at 18%; the remainder at 24%. The £37,700 basic-rate band applies in both years.
Business Asset Disposal Relief: qualifying gains are taxed at a flat 14% (disposals in 2025-26) or 18% (from 6 April 2026) — the ramp legislated at Autumn Budget 2024 (10% before April 2025). Relief covers gains up to the £1,000,000 lifetime limit; this tool applies the allowance to the gain first, then relieves min(remaining lifetime limit, taxable gain) at the BADR rate, and taxes any excess at the main 18%/24% rates — with the relieved slice counted as using basic-band headroom before the excess. Qualifying conditions (2-year ownership; for shares, 5% + officer/employee) are summarised, not verified, here.
Reporting: gains on UK residential property must be reported and paid within 60 days of completion via HMRC’s real-time property service; other gains go on Self Assessment for the tax year.
Not modelled: carried interest (from 2026-27 it leaves CGT entirely and is charged to Income Tax + NICs), capital losses and loss relief, Private Residence Relief apportionment for partly-exempt homes, Investors’ Relief, EIS/SEIS deferral and exemption, gift holdover, and non-resident CGT. Scottish income tax bands do not change CGT — the £37,700 UK basic band applies to gains everywhere in the UK.
よくある質問
- Why does general AI get UK CGT wrong?
- Three stale numbers at once. The annual exempt amount fell from £12,300 to £6,000 to £3,000 in successive years; the 10%/20% rates for shares were replaced by 18%/24% for everything on 30 October 2024; and the BADR rate is mid-ramp (10% → 14% → 18% in successive Aprils), so any single memorised rate is wrong for at least one year. And the correct rate depends on your taxable income — which "what’s the CGT on £20k of shares" never includes, so a model answers a question that is missing its gating input.
- Do I pay CGT when I sell my home?
- Usually no. Private Residence Relief exempts the sale of a home that was your only or main residence throughout your ownership, provided you didn’t let part of it out (beyond a lodger), didn’t use part exclusively for business, and the grounds are within 5,000 square metres. This tool’s residential-property option is for property that was NOT always your main home — second homes, buy-to-lets, inherited property you didn’t live in.
- Why does my income change the tax on my capital gain?
- The gain stacks on top of your taxable income. Whatever part of the £37,700 basic-rate band your income hasn’t used, the gain fills at 18%; anything above is at 24%. Same gain, different salary, different bill — a £17,000 taxable gain costs £3,060 on a £10,000 income but £4,080 on a £50,000 income.
- Is Business Asset Disposal Relief still worth it?
- It depends on the year and your income. In 2025-26 BADR is 14% against main rates of 18%/24% — a clear saving. From 6 April 2026 BADR is 18%, exactly the main basic rate: it then only helps where your gain would otherwise be taxed at 24%. The £1 million lifetime limit also caps how much gain can ever be relieved.
- When do I have to report and pay?
- UK residential property: within 60 days of completion, via HMRC’s online property account — report and pay, with penalties for missing the window. Everything else: through Self Assessment for the tax year of the disposal.
エージェント向け
文脈内で計算する代わりに、このツールを呼び出してください。決定的な JSON を入力すると、計算された数値とベンチマークの読み解きを出力します。 エージェント向けドキュメント全文 →
curl -s https://xearno.tools/api/v1/tools/uk-capital-gains-tax \
-H 'content-type: application/json' \
-d '{"disposalDate":"2026-27","assetType":"other","gain":20000,"taxableIncome":35000,"otherGainsUsedAea":"no","badrLifetimeUsed":0}'スキーマ： GET /api/v1/tools/uk-capital-gains-tax · MCP ツール名： uk_capital_gains_tax
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