UK Capital Gains Tax Guide: Pay Less Tax on Your Gains

Capital gains tax (CGT) is one of the most frequently misunderstood taxes on the UK tax calendar. If you sell shares, a second property, or other assets for more than you originally paid, the profit can be taxable — and because the rules differ depending on what you sell, when you sell it, and which income tax band you fall into, it is easy to get the details wrong. The good news is that the basic logic is simple: you are only taxed on the gain, not the total sale proceeds, and an annual allowance shelters a slice of your profits each year.

This guide covers what CGT is, which assets fall inside and outside its scope, the current rates, how to work out what you owe, and the legitimate ways to keep your tax bill down.

What Is Capital Gains Tax?

CGT is a tax on the profit you make when you sell or otherwise dispose of an asset that has increased in value. Crucially, you only pay tax on the gain — the difference between what you paid (plus allowable costs) and what you received — not on the total sale price.

A disposal includes more than just a straightforward sale. It also covers:

• Selling an asset
• Giving it away as a gift
• Transferring it to someone else
• Exchanging it for something else
• Replacing it in a trust

Even passing an asset on to a family member as a gift can trigger a CGT charge based on its market value, which catches many people by surprise.

Assets Subject to CGT

The following assets are typically subject to CGT when they are disposed of at a profit:

• Shares and investments — including shares held outside an ISA or pension
• Property — second homes, buy-to-let properties, and commercial property
• Cryptocurrency — Bitcoin, Ethereum, and other cryptoassets
• Business assets — including intellectual property and goodwill
• Personal possessions — items worth over £6,000 (excluding your car)

HMRC treats cryptoassets as property for CGT purposes, which means buying and selling them — or swapping one crypto for another — can each give rise to a taxable gain.

Assets Exempt from CGT

Not everything you sell is subject to CGT, and knowing what is exempt can spare you both tax and anxiety. The following are outside the scope of CGT:

• Your main home — private residence relief covers your primary residence
• Cars — all cars are exempt, regardless of profit
• ISAs and pensions — gains within these wrappers are tax-free
• £1,000 personal allowance — a small gains allowance for personal possessions
• Gifts to spouse or civil partner — transfers between spouses are tax-free
• UK government gilts and Premium Bonds — exempt from CGT
• Betting and lottery winnings — not subject to CGT

The exemptions on your main home and on ISAs are the two most valuable for most people.

CGT Rates (2024/25)

The rate you pay depends on your income tax band, and for 2024/25 the headline rates are as follows:

Your income tax band is determined by your total taxable income, with the gain itself added on top — meaning a large gain can push you from the basic into the higher rate band and change the rate that applies to some of it.

Annual Exempt Amount

Every UK resident gets an annual CGT exempt amount. For the 2024/25 tax year, this is £3,000.

If your total gains for the year are below £3,000, you pay no CGT at all. If your gains exceed £3,000, you only pay CGT on the amount above this threshold. Once the allowance is used up it is gone — there is no way to carry it forward, which is why using or losing it each year is a recurring theme in tax planning.

How to Calculate CGT

The calculation follows a relatively small number of steps:

1. Work out your gain: Sale price - Purchase price - Allowable costs
2. Apply your annual exemption: Subtract £3,000 from your total gains
3. Determine your tax rate: Based on your income tax band
4. Calculate the tax: Taxable gain × CGT rate

Allowable costs can reduce your gain and therefore your bill. They include:

• Stamp duty and legal fees when buying
• Estate agent and conveyancing fees when selling
• Cost of improvements (not routine maintenance)
• Share dealing commission

There are also costs you cannot deduct — mortgage interest and routine maintenance do not count as allowable.

Reporting and Paying CGT

How and when you report a gain depends on what you sold, and the two main routes are quite different.

Property Sales

You must report and pay CGT on property sales within 60 days of completion. Use the HMRC online real-time CGT service. If you miss the deadline, you may face penalties and interest.

Shares and Other Assets

For shares and most other assets, gains are reported through your annual Self Assessment tax return. The deadline for online filing is 31 January following the end of the tax year, and any CGT due must be paid by the same date.

This distinction catches people out — a property disposal cannot wait for the Self Assessment deadline, because the 60-day rule is much tighter.

Ways to Reduce Your CGT Bill

There are several legitimate, entirely legal strategies for reducing or eliminating CGT. None of them require any exotic arrangements — they are mostly about timing and using the allowances the tax system already gives you.

1. Use Your Annual Exempt Amount Each Year

You cannot carry forward unused annual exemption. Use it or lose it each tax year. Consider crystallising gains up to £3,000 each year.

2. Transfer Assets to Your Spouse or Civil Partner

Transfers between spouses are CGT-free. If one partner is a basic rate taxpayer and the other is higher rate, transferring assets before selling can result in a lower combined tax bill.

3. Offset Losses Against Gains

If you have assets at a loss, consider selling them to crystallise the loss. Losses offset gains in the same tax year, and unused losses can be carried forward indefinitely.

4. Invest Through an ISA

Gains within an ISA are completely tax-free. Use your £20,000 annual ISA allowance to shelter investments from CGT.

5. Business Asset Disposal Relief

If you sell a qualifying business, you pay 10% CGT on the first £1 million of gains (lifetime limit). This is available to company directors and shareholders with at least 5% of shares and voting rights.

6. Timing Your Sales

Consider selling assets at the start of a new tax year to maximise use of your annual exemption. Spreading sales over multiple tax years can also help.

Worked Example

An example brings the calculation together. Sarah sells shares she bought for £30,000 and sells them for £50,000. She pays £500 in transaction fees.

Step 1: Calculate the gain

£50,000 - £30,000 - £500 = £19,500 gain

Step 2: Apply annual exemption

£19,500 - £3,000 = £16,500 taxable gain

Step 3: Calculate CGT

Sarah is a higher rate taxpayer (24% CGT rate):

£16,500 x 24% = £3,960 CGT

If Sarah had sold £3,000 of gains in the previous tax year using her annual exemption, her CGT for the current year would have been lower, because that first £3,000 of profit each year is sheltered.

Practical Tips

A few habits make a real difference over time, whatever your situation:

• Use your ISA — shelter as much as possible within your £20,000 annual allowance
• Harvest losses — sell underperforming assets to offset gains elsewhere
• Time your sales — spread disposals across tax years to use multiple annual exemptions
• Transfer to spouse — move assets before selling to use their lower tax rate or annual exemption
• Report on time — property sales must be reported within 60 days or you face penalties
• Keep records — maintain clear records of purchase dates, prices, and costs for at least 6 years
• Consider bed and ISA — sell assets and immediately repurchase within an ISA to reset the cost base

References

• HMRC — Capital Gains Tax
• GOV.UK — Capital Gains Tax Rates and Allowances
• HMRC — Report and Pay CGT on Property
• MoneyHelper — Capital Gains Tax

A Final Word

Capital gains tax need not be daunting. The most useful approach is to keep a record of what you paid for assets, use the annual exempt amount deliberately each year, and shelter what you can inside ISAs. If you get the basics right, a substantial portion of your profits can stay with you rather than going to the taxman — and for larger gains or property sales in particular, a qualified accountant or financial adviser can help you plan the timing before you commit.