HMRC Capital Gains Tax Estimator (UK)
Use this quick calculator to estimate UK Capital Gains Tax (CGT) on a disposal. It follows the standard HMRC flow: gain, losses/reliefs, annual exempt amount, then CGT rates.
How HMRC capital gains tax is calculated
Capital Gains Tax is usually due when you sell or dispose of an asset for more than its allowable base cost. In broad terms, HMRC starts with your gain, then allows you to deduct certain costs, losses, and reliefs before applying CGT rates. This page gives you a practical way to estimate the result before filing.
The calculator above is designed for individuals making a straightforward disposal. It is especially useful for second homes, buy-to-let property, shares, and other chargeable assets where CGT may apply.
What this calculator includes
1) Gross gain calculation
Your gross gain starts with disposal proceeds minus allowable costs. Allowable costs typically include purchase price, buying fees, selling fees, and qualifying capital improvements.
2) Losses and reliefs
After the gross gain, you can offset eligible losses brought forward and reliefs. This reduces the amount exposed to tax. The calculator treats these as direct deductions from the gain.
3) Annual exempt amount
HMRC gives individuals an annual tax-free CGT allowance (annual exempt amount). Once deducted, only the remaining taxable gain is subject to CGT rates.
4) Rate split using your income band
CGT rates depend on both asset type and your remaining basic rate band. Part of the gain may be taxed at the lower rate and the rest at the higher rate, based on your taxable income for the year.
Allowable costs checklist
- Purchase price paid for the asset
- Stamp Duty Land Tax (where applicable on acquisition)
- Legal and conveyancing fees on purchase and sale
- Estate agent or broker fees for disposal
- Capital improvements (for example, an extension or structural upgrade)
- Costs of establishing, defending, or improving title
Routine maintenance and general repairs are usually not capital improvements for CGT purposes. Keep records and invoices to support each claim.
Rates used in this HMRC capital gains calculator
The estimator uses a common individual-rate approach:
- Residential property: 18% in basic rate band, 24% above it
- Other chargeable assets: 10% in basic rate band, 20% above it
Rates and thresholds can change over time, and certain assets may have special treatment. Always verify the latest HMRC guidance for your tax year.
Worked example
Suppose you sell a rental flat for £350,000. You bought it for £220,000, spent £8,000 on legal and buying costs, paid £6,000 in selling costs, and made £20,000 of qualifying improvements. Your gross gain is:
£350,000 - (£220,000 + £8,000 + £6,000 + £20,000) = £96,000
If you have £5,000 of brought-forward losses and £3,000 annual exempt amount, taxable gain becomes £88,000. Then your income position decides how much is taxed at lower vs higher CGT rates.
Important reliefs not fully automated
Some CGT outcomes depend on rules too detailed for a single estimator. You may need specialist advice if any of these apply:
- Private Residence Relief (PRR)
- Business Asset Disposal Relief (BADR)
- Gift Hold-Over Relief or Rollover Relief
- Non-resident CGT rules and rebasing options
- Trusts, companies, or jointly owned assets with complex splits
Common filing mistakes to avoid
- Forgetting to include acquisition and disposal fees
- Claiming repair costs as capital improvements
- Not reporting gains by the required deadline
- Using the wrong annual exemption or tax-year rates
- Ignoring prior-year losses that could reduce tax
FAQ
Do I pay CGT on selling my main home?
Often no, because of Private Residence Relief, but partial charges can apply in some circumstances. Do not assume full exemption without checking your facts.
Can I include stamp duty and legal fees?
Yes, costs directly related to purchase and sale are generally allowable and can reduce your gain.
Can I use losses from prior years?
Yes, where valid and available, brought-forward losses can be offset against gains before tax is calculated.
Is this calculator the same as HMRC’s own service?
No. This is an educational estimator to help planning. Your official liability should be confirmed through HMRC filing and, where needed, qualified advice.
Final note
A good HMRC capital gains calculator helps you plan cash flow, set aside tax, and avoid surprises. Use the estimate early, keep accurate records, and review your position before year-end so you can take legitimate steps to reduce tax efficiently.