What this calculator does
Takes disposal proceeds, cost basis, allowable costs, the taxpayer's income band, and asset type (residential property vs other assets). Returns the net gain, taxable gain after the annual exempt amount, and CGT due.
The formula
Net gain = Proceeds − Cost basis − Allowable costs Taxable gain = max(0, Net gain − Annual Exempt Amount) 2025/26 Annual Exempt Amount: £3,000 Tax rates (2025/26): Other assets: Basic rate 10%, Higher/Additional rate 20% Residential property: Basic rate 18%, Higher/Additional rate 24% BADR (qualifying business disposals): 10% up to £1,000,000 lifetime limit Where income + gains straddles the basic/higher rate boundary, gains in the basic rate band pay the lower rate; the rest pay the higher rate. Basic rate band upper limit: £50,270 (personal allowance £12,570 + £37,700)
Assumptions
- UK resident for the full tax year.
- No carried-forward losses applied.
- No principal private residence (PPR) relief.
- No entrepreneurs' relief complexities beyond Business Asset Disposal Relief (BADR).
- Income figure entered is total taxable income before gains.
Data sources
| Figure | Value used | Source | Last checked |
|---|---|---|---|
| Annual Exempt Amount | £3,000 | HMRC — Capital Gains Tax allowances | May 2026 |
| Basic rate (other assets) | 10% | HMRC — Capital Gains Tax rates | May 2026 |
| Higher rate (other assets) | 20% | HMRC — Capital Gains Tax rates | May 2026 |
| Basic rate (residential) | 18% | HMRC — Capital Gains Tax rates | May 2026 |
| Higher rate (residential) | 24% | HMRC — Capital Gains Tax rates | May 2026 |
| BADR rate | 10% | HMRC — Business Asset Disposal Relief | May 2026 |
Limitations
- Does not model principal private residence (PPR) relief or letting relief.
- Does not handle carried-forward losses.
- Does not cover non-resident CGT.
- The 60-day reporting window for residential property sales is not enforced by the calculator.
Worked example
Basic rate taxpayer sells shares for £25,000, cost basis £10,000, £200 dealing costs.
Net gain: £25,000 − £10,000 − £200 = £14,800 Taxable gain: £14,800 − £3,000 = £11,800 CGT due: £11,800 × 10% = £1,180
Changelog
| Date | Change |
|---|---|
| May 2026 | Initial publication |