Capital Gains Tax Calculator UK

How the Capital Gains Tax Calculator Works

Enter your sale proceeds, what you paid for the asset, any allowable costs and your annual income. The calculator deducts costs to find gain, subtracts £3,000 annual exempt amount, then stacks taxable gain on top of your income to work out how much falls in each rate band.

The core formula, gain = sale price minus purchase price minus allowable costs. Allowable costs include broker fees, stamp duty paid on purchase, legal fees and capital improvements, but not maintenance or mortgage interest.

CGT Rates and Allowance for 2026/27

Since October 2024 Budget rates are unified across asset types. For 2026/27:

• 18 percent on gains falling within your unused basic rate band
• 24 percent on gains above it
• £3,000 annual exempt amount per person, which cannot be carried forward
• Business Asset Disposal Relief at 18 percent on qualifying gains up to a £1 million lifetime limit, up from 14 percent last year

The same 18 and 24 percent rates now apply to shares, funds, crypto and residential property alike. The old 10 and 20 percent rates on shares ended on 30 October 2024, so any figures you remember from before then are out of date.

Which band you pay depends on your income. Take your taxable income after personal allowance, see how much of £37,700 basic rate band remains and that much of your gain is taxed at 18 percent with the rest at 24. Earn over £50,270 and the whole taxable gain sits at 24 percent.

Worked Example

Salary of £40,000 and a £23,000 gain on shares:

• Taxable gain after the £3,000 allowance: £20,000
• Taxable income: £40,000 - £12,570 = £27,430
• Remaining basic rate band: £37,700 - £27,430 = £10,270
• First £10,270 of gain at 18 percent: £1,849
• Remaining £9,730 at 24 percent: £2,335
• Total CGT: £4,184

Note how a pension contribution that lowered taxable income would have shifted more of gain into the 18 percent band, saving 6p per pound moved.

The 60 Day Property Deadline

Selling a UK residential property that is not fully covered by main residence relief triggers a separate reporting rule, the gain must be reported and the tax paid within 60 days of completion through HMRC’s online property service. This sits apart from Self Assessment and missing it brings automatic penalties starting at £100. Shares, funds and crypto follow the normal route instead, reported through Self Assessment by 31 January after the tax year ends.

Your main home is usually exempt entirely under Private Residence Relief, though letting it out, using part exclusively for business or long absences can create a taxable slice.

Legitimate Ways to Reduce a CGT Bill

Several standard planning moves remain fully available. Assets transfer between spouses and civil partners with no CGT, which lets a couple use two £3,000 allowances and the lower earner’s 18 percent band. Selling in stages across two tax years uses two allowances. Losses on other investments offset gains and unused losses carry forward indefinitely provided they are reported within four years. And anything held inside an ISA or pension is outside CGT altogether, which is why filling ISA allowance each year is the simplest long term defence.

CGT interacts with your wider tax position, so for large disposals it is worth speaking to an accountant or tax adviser before you sell rather than after. This page is information rather than personal tax advice.