How the calculation works
- Add your net CFD gains to any other capital gains for the tax year.
- Subtract the £3,000 annual exempt amount.
- Work out how much of your basic-rate band is unused after your income.
- Gains within that unused band are taxed at 18%; the rest at 24%.
Worked example
Income £40,000 and CFD gains £8,000: taxable gains are £5,000. Income uses £27,430 of the £37,700 basic-rate band, leaving £10,270 — enough to cover the whole £5,000 at 18%, so the estimate is £900.
What this calculator doesn't do
- Spread betting (generally exempt) or trading treated as income
- Personal Allowance tapering for incomes over £100,000
- Losses brought forward from earlier years — subtract those from your gains first
- Non-UK residents
For the full rules see our forex tax guide, and consider professional advice if your situation is complex.
Frequently asked questions
Does this calculator work for spread betting?
Spread betting profits are generally exempt from CGT for UK residents, so enter only CFD and other taxable gains.
Which income should I enter?
Your total taxable income for the tax year before the Personal Allowance — for example salary, self-employed profits and taxable interest.
CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. Most retail investor accounts lose money when trading these products. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Content is general information, not financial or tax advice. This calculator gives a simplified estimate using standard 2026/27 thresholds (Personal Allowance £12,570, basic-rate band £37,700, annual exempt amount £3,000, CGT rates 18% and 24%). It ignores Personal Allowance tapering above £100,000, Scottish income tax bands for the band calculation, and other reliefs. Not tax advice.