UK Capital Gains Tax Calculator

A capital gains tax calculator UK helps you estimate the Capital Gains Tax (CGT) you may owe when you sell or dispose of an asset such as shares, cryptocurrency, a second property, or a business for more than you paid for it. The calculator above takes your total gain, the annual tax-free allowance you have left, and your tax band, then works out how much of your profit is taxable and how much tax could be due for the 2025/26 tax year. This page explains what each input and output means, the current rates and allowance, how your income affects your rate, when you have to report and pay, and where the rules for residential property differ. It is written for UK traders and investors who want a clear, honest picture before tax time. Last reviewed 2026.

What Capital Gains Tax is in the UK

Capital Gains Tax is a tax on the profit, or gain, you make when you dispose of an asset that has risen in value. You are taxed on the gain, not on the total amount of money you receive. If you buy shares for 5,000 pounds and sell them for 9,000 pounds, your gain is 4,000 pounds, and only that 4,000 pounds is looked at for CGT. Disposing includes selling, giving an asset away, swapping it for something else, or getting compensation for it. Common assets that fall inside CGT include listed and unlisted shares, units in funds, cryptoassets like Bitcoin and Ethereum, second homes, buy-to-let property, and business assets. Your main home is usually exempt through Private Residence Relief, and everyday personal items below a set value are often outside CGT. Gains inside an ISA or a pension are not subject to CGT at all, which is one reason many long-term investors use those wrappers.

CGT is separate from Income Tax, but the two connect. Your income for the year is worked out first, and it sets how much room is left in your basic rate band. Whatever gain then sits on top of that income is taxed at the CGT rate for the band it falls into. This is why two people with the same gain can owe very different amounts of tax.

How the calculator inputs and outputs work

The calculator above is a quick estimate tool. It asks for three inputs and returns five outputs. Here is what each one means so you can enter accurate figures and read the result correctly.

1. Total Gain: the profit on your disposal after costs. Take your sale proceeds, subtract what you paid, and subtract allowable costs such as broker fees, dealing charges, and, for property, buying and selling costs. If you sold several holdings, add the gains together and subtract any losses.
2. Annual Exempt Amount Left: how much of your 3,000 pounds tax-free allowance is still unused this tax year. If you have made no other gains, enter 3,000. If you have already used some, enter what remains. The allowance cannot be carried to another year.
3. Tax Band (basic or higher): whether your gain is taxed at the basic rate or the higher rate. This depends on your taxable income. If you are unsure, pick the band your income falls into, and read the worked examples below for gains that cross the boundary.

The outputs then show: Taxable Gain, which is your total gain minus the allowance you had left; CGT Owed, the estimated tax on that taxable gain at your rate; Allowance Used, how much of the 3,000 pounds the disposal soaked up; Net Gain After Tax, your gain minus the estimated CGT so you can see what you actually keep; and Rate Applied, the percentage used in the sum. Treat the CGT Owed figure as a guide, not a final bill, because the calculator applies a single band and cannot see your full income picture or every relief you may qualify for.

CGT rates and the allowance for 2025/26

The October 2024 Budget raised the main CGT rates. For disposals on or after 30 October 2024, the rate on most assets, including shares and crypto, went from 10 percent to 18 percent in the basic band and from 20 percent to 24 percent in the higher band. Those higher rates carry through the whole 2025/26 tax year. The annual exempt amount stayed at 3,000 pounds, down from 6,000 pounds in 2023/24 and 12,300 pounds a few years earlier, so more modest gains now fall into tax than before. The table below sets out the key figures and how they changed.

How your income decides your CGT band

CGT is not charged in a vacuum. HMRC stacks your gain on top of your taxable income for the year. For 2025/26 the basic rate band ends at 50,270 pounds of taxable income. Whatever space is left between your taxable income and 50,270 pounds is the amount of gain that can be taxed at the lower 18 percent rate. Any gain above that point is taxed at 24 percent. So a large gain often gets split: part at 18 percent, part at 24 percent. The calculator above uses one band at a time, so if your gain straddles the boundary, the third worked example below shows how to split it by hand for a more accurate answer.

Three worked examples

Example 1: basic rate taxpayer selling shares

Tom has a modest salary that leaves plenty of room in his basic rate band. He sells shares for a gain of 8,000 pounds and has his full 3,000 pounds allowance available. Taxable gain is 8,000 minus 3,000, which is 5,000 pounds. At the basic rate of 18 percent, CGT owed is 900 pounds. His allowance used is 3,000 pounds and his net gain after tax is 8,000 minus 900, which is 7,100 pounds. Rate applied is 18 percent.

Example 2: higher rate taxpayer with a crypto gain

Priya is a higher rate taxpayer whose income already fills the basic band. She sells cryptocurrency for a gain of 20,000 pounds with her full 3,000 pounds allowance left. Taxable gain is 20,000 minus 3,000, which is 17,000 pounds. At the higher rate of 24 percent, CGT owed is 4,080 pounds. Allowance used is 3,000 pounds and net gain after tax is 20,000 minus 4,080, which is 15,920 pounds. Rate applied is 24 percent.

Example 3: a gain that straddles both bands

Sarah has taxable income of 45,000 pounds for the year. The basic rate band ceiling is 50,270 pounds, so she has 5,270 pounds of basic band room left. She makes a gain of 18,000 pounds on shares and has her full 3,000 pounds allowance. Taxable gain is 18,000 minus 3,000, which is 15,000 pounds. The first 5,270 pounds of that gain is taxed at 18 percent, which is 948.60 pounds. The remaining 9,730 pounds is taxed at 24 percent, which is 2,335.20 pounds. Total CGT owed is about 3,283.80 pounds, and her net gain after tax is roughly 14,716 pounds. This is why picking a single band can understate or overstate your bill when a gain crosses the boundary.

Reporting and paying your CGT

How and when you report depends on the asset. For most assets, such as shares and crypto, you report gains through your Self Assessment tax return, or you can use HMRC's real-time Capital Gains Tax service during the year. The Self Assessment deadline for online returns is 31 January after the end of the tax year, and any tax due is normally payable by that same date. The UK tax year runs from 6 April to 5 April, so gains made in 2025/26 fall on the return due by 31 January 2027. Residential property has a much tighter rule: if CGT is due on a UK residential property disposal, you usually have to report and pay within 60 days of completion using a separate online property return. Missing these deadlines can trigger penalties and interest, so diarise them the moment you sell.

Keep records even when no tax is due. HMRC can ask you to show how you worked out a gain, and losses you report can be carried forward to reduce future gains, but usually only if you have registered them within the time limit. Good records include purchase and sale contract notes, dates, quantities, fees, and, for crypto, the sterling value at the time of each transaction.

Residential property and special cases

Residential property that is not your main home, such as a buy-to-let or a second home, is taxed at 18 percent in the basic band and 24 percent in the higher band for 2025/26. The 28 percent higher property rate that existed in earlier years was cut to 24 percent from April 2024, so property and other assets now line up at the same headline rates. Even so, property is treated differently in practice: the 60-day reporting rule applies, Private Residence Relief can reduce or remove the gain on a home you have lived in, and lettings relief may apply in limited cases. Business owners may qualify for Business Asset Disposal Relief, which taxes qualifying gains at 14 percent for 2025/26, up from 10 percent, subject to a lifetime limit. These reliefs have detailed conditions, so the simple calculator above will not capture them. Treat any asset with special rules as a case to check with a professional.

Tips and common mistakes

A few habits keep your CGT estimate honest and your future filing painless.

• Do not forget to subtract allowable costs. Broker commissions, dealing fees, and for property the legal and estate agent costs all reduce your gain.
• Offset your losses. Losses in the same year reduce your gains before the allowance is applied, and unused losses can often be carried forward if reported in time.
• Watch the band boundary. A large gain can push part of your profit into the 24 percent rate even if your salary sits in the basic band.
• Remember crypto is inside CGT. Selling, swapping one coin for another, or spending crypto can all be disposals in sterling terms.
• Do not assume the 3,000 pounds allowance rolls over. If you do not use it in the tax year, it is gone.
• Mind the 60-day property deadline, which is separate from and much earlier than the Self Assessment deadline.

Capital Gains Tax rewards good record keeping. The traders who struggle at tax time are usually the ones piecing together buy prices, sale dates, and fees from scattered statements months later. If you log every trade as you go, with the date, size, entry, exit, and costs, your gain for the year is a simple sum and your CGT estimate becomes trustworthy. That is exactly what a clean trade log on OneTradeJournal is built for: a dated, honest record of what you actually did, so that when the tax deadline comes you can hand over clear numbers instead of a shoebox of screenshots. Keep the log tidy through the year, run your figures through the calculator above for a rough guide, and confirm the final amount with a qualified tax professional before you file.