Calculate UK Capital Gains Tax on selling investments, shares, property, or other assets. Works with annual exemption thresholds and current tax rates for 2024/25. Calculate your tax liability instantly.
Capital Gains Tax (CGT) applies when you sell an asset for more than you paid for it. The "gain" is the difference between selling price and original cost, minus selling costs like commission and fees. Every UK taxpayer gets an annual exemption (£3,000 in 2024/25) meaning you only pay CGT on gains exceeding this threshold. CGT rates depend on your income tax band: basic rate taxpayers pay 10% on shares/standard assets or 18% on residential property; higher rate taxpayers pay 20% on shares or 28% on residential property. Married couples can each claim separate exemptions (£6,000 combined) by splitting asset sales. You must report CGT to HMRC within four years of tax year end. Principal Private Residence (PPR) relief means your main home is usually exempt from CGT. Some assets like ISAs are CGT-free. You can offset losses from other assets against gains to reduce taxable gains.
Use your annual exemption efficiently—if you have £8,000 gain and £3,000 exemption, you pay tax on £5,000. If married, split asset sales with spouse to use both exemptions (£6,000 combined). Offset losing investments against winning ones—if you have £15,000 gain and £4,000 loss on another asset, taxable gain is £11,000. Hold investments over one year as some reliefs apply to longer-held assets. Consider timing: if your gain pushes you into higher tax bracket, deferring to next tax year (April) might lower your rate. Gift appreciated assets to spouses or registered charities to avoid CGT entirely. Use ISAs for new investments to shield future gains from tax. Invest in EIS (Enterprise Investment Scheme) or SEIS (Seed EIS) schemes which offer CGT exemption on gains if held five years. Finally, keep meticulous records of purchase prices and costs as HMRC requires evidence for CGT calculations.
HMRC has sophisticated systems detecting unreported gains through bank deposits, property records, and transaction reporting from brokers. Penalties for undeclared gains range from 20% to 100% of unpaid tax plus interest accruing at 8.75% annually. If gains are "careless" (unintentional errors) penalties are 30-40% of unpaid tax. If "deliberate" tax evasion, penalties reach 50-100% plus potential criminal prosecution, unlimited fines, and prison sentences up to seven years. You must report gains within one year of tax year end or face automatic penalties. Even small unreported gains compound if repeated multiple years. The safest approach is declaring all gains accurately and claiming all available reliefs and exemptions.
You don't pay CGT immediately upon sale—rather you report gains in your self-assessment tax return (by January 31st following the tax year). Payment is due when you submit the return. So if you sell shares in March 2024, you report this in your tax return due January 31, 2025, and pay then. If you have significant gains and expect to owe more than £3,000, you can make a voluntary Payment on Account to avoid interest. If gains tip you into higher tax bracket you can claim income averaging (farmers can average over five years). Having a tax accountant prepare your return ensures you claim all available relief and potentially save more tax than the accountant costs.
Sale price £50,000, original cost £30,000 = £20,000 gain. Less annual exemption £3,000 = £17,000 taxable. At basic rate 10% = £1,700 CGT owed. Net proceeds after tax: £48,300.
If both listed as owners they can split £25,000 gain = £12,500 each. Each claims £3,000 exemption. Taxable per person £9,500. If higher rate = 28% × £9,500 × 2 = £5,320 total CGT (versus £5,600 if one owned it entirely).
Share portfolio gain of £18,000 and property sold at £4,000 loss. Net gain £14,000 less £3,000 exemption = £11,000 taxable × 10% = £1,100 CGT.
Track cost basis meticulously including original purchase price, acquisition fees, and transaction costs as these reduce taxable gains. Use average cost method for shares purchased at different prices rather than FIFO or LIFO which can increase gains. Gift appreciated assets before sale to avoid CGT if family member in lower tax bracket. Plan large asset sales across multiple years to use annual exemptions more efficiently. Consider fundamental tax efficiency: ISAs shield investments from CGT entirely (use before investing taxably). Pension contributions reduce taxable income and create CGT-free growth. Use spousal exemptions strategically—unmarried partners don't get relief so consider marriage planning implications. Document all costs including professional fees, advertising, and repairs as these reduce gains. Time sales to maximize losses offsetting in down market years. Keep six-year records of all transactions in case HMRC queries CGT returns.