UK Capital Gains Tax Calculator (2025-26 & 2026-27)
uk_capital_gains_taxCapital Gains Tax on shares, crypto, property, or a business sale — current £3,000 allowance, the 18%/24% rate split driven by your income, and the BADR 14% → 18% ramp. 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.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| gain | No | Total gain on the disposal (£) Proceeds minus what you paid minus allowable costs (buying/selling fees, improvement costs). The gain, not the sale price. | |
| assetType | No | What are you selling? BADR (Business Asset Disposal Relief) needs, broadly: 2 years of ownership, and for company shares at least 5% of shares and votes while being an officer or employee — check the full conditions. Selling the home you’ve always lived in? Usually NO CGT at all (Private Residence Relief) — this tool is for property that was never, or not always, your main home. | other |
| disposalDate | No | When are you disposing (tax year)? The BADR rate steps 14% → 18% at this boundary (6 April 2026) — the disposal date IS a rate input now, not admin detail. Main 18%/24% rates and the £3,000 allowance are the same in both years. | 2026-27 |
| taxableIncome | No | Your taxable income this year (£) Income AFTER the personal allowance — roughly your salary minus £12,570. This is the hidden input: the gain stacks on top of it, and it decides how much falls in the basic band at 18% vs above it at 24%. | |
| badrLifetimeUsed | No | BADR lifetime relief already claimed (£) Only matters for BADR disposals. Gains you have already claimed BADR on, ever — the relief has a £1 million lifetime limit. | |
| otherGainsUsedAea | No | Already used the £3,000 allowance this year? The annual exempt amount is per tax year across all your disposals, not per disposal. | no |