UK Capital Gains Tax Calculator

About UK Capital Gains Tax Calculator

How Is UK Capital Gains Tax Calculated?

CGT is applied to the net gain on a chargeable disposal, after allowable costs, the annual exempt amount, and any basic rate band remaining after your income. The formula is:

Taxable Gain = Sale Price - Purchase Price - Allowable Costs - Annual Exempt Amount

The taxable gain is stacked on top of your taxable income. Any portion that falls inside your remaining basic rate band is taxed at 18%. The rest is taxed at 24%. HMRC confirmed in its Autumn Budget 2025 Tax Information Note that the 18%/24% main rates are held for 2026/27 alongside the £3,000 annual exempt amount.

Worked example (shares): You buy shares for £20,000 and sell for £35,000. Broker fees total £200. Your taxable income for the year is £40,000 (well inside the basic rate band).

• Net gain: £35,000 - £20,000 - £200 = £14,800
• After exempt amount: £14,800 - £3,000 = £11,800 taxable
• Basic rate band remaining: £50,270 - £40,000 = £10,270
• £10,270 at 18% = £1,848.60
• £1,530 at 24% = £367.20
• Total CGT: £2,215.80. Effective rate on the net gain: 15.0%

Worked example (buy-to-let property): You bought a BTL flat for £180,000 in 2014 and sold it for £260,000 in 2026. Purchase costs (SDLT, legal) were £3,500. Sale costs (agent, solicitor) were £5,200. You earn £55,000 PAYE, so all of the gain falls above the basic rate band.

• Net gain: £260,000 - £180,000 - £3,500 - £5,200 = £71,300
• After exempt amount: £71,300 - £3,000 = £68,300 taxable
• Basic band remaining: £0 (income already above £50,270)
• £68,300 at 24% = £16,392 CGT
• Must be reported and paid within 60 days of completion via HMRC's online service

2026/27 UK CGT Rates and Allowances

Main rates are unchanged from 2025/26, but Business Asset Disposal Relief (BADR) steps up from 14% to 18% from 6 April 2026. Investors' Relief tracks BADR and moves to 18% on the same date.

Band / Relief	2025/26 Rate	2026/27 Rate	Notes
Basic rate (within remaining band)	18%	18%	All assets since 30 Oct 2024
Higher / additional rate	24%	24%	Residential and other assets aligned
Business Asset Disposal Relief	14%	18%	Up to £1M lifetime limit
Investors' Relief	14%	18%	Lifetime limit cut to £1M from Oct 2024
Trusts (after £1,500 AEA)	24%	24%	Trustees pay the top rate on all gains
Annual exempt amount (individuals)	£3,000	£3,000	Frozen since 2024/25

The AEA was cut from £12,300 in 2022/23 to £6,000 in 2023/24 and then to £3,000 in 2024/25. According to HMRC's CGT commentary, the reduction pulled an additional 260,000 taxpayers into CGT in 2023/24 alone. The headline shift from 10%/20% non-property rates to 18%/24% took effect on 30 October 2024 and caught traders, founders, and crypto holders alike.

What Counts as an Allowable Cost?

Anything spent to acquire, improve, or dispose of the asset can be deducted, provided it is capital in nature and not already deducted against income tax. HMRC's CG15150 guidance lists the main categories:

• Acquisition costs: purchase price, stamp duty or SDLT, broker commissions, solicitor and survey fees
• Enhancement costs: extensions, renovations, new kitchens, structural repairs that improve the asset (not routine maintenance)
• Disposal costs: estate agent fees, solicitor fees, marketing, valuation fees
• Incidental costs: professional advice directly related to the transaction

You cannot deduct mortgage interest, routine repairs, insurance, or the value of your own time. For SDLT on a purchase, use the stamp duty calculator to check the figure before you add it to the cost base.

UK CGT vs US Capital Gains Tax

The UK and US tax long-term investment gains very differently. US short-term gains (assets held under one year) are taxed as ordinary income up to 37%, while long-term gains (over one year) get preferential rates. The UK has no holding-period distinction - the same rate applies regardless of how long you held the asset.

Feature	UK (2026/27)	US (2025 long-term)
Annual tax-free amount	£3,000 AEA	None explicit (0% bracket instead)
Main rates (individuals)	18% / 24%	0% / 15% / 20%
0% band (single filer)	Not applicable	Up to $48,350 taxable income
20% band (single filer)	Not applicable	Over $533,400 taxable income
Main home exemption	Principal Private Residence - unlimited	Section 121 - up to $250K single / $500K joint
Holding period effect	None	Under 1 year = ordinary income rates (up to 37%)
Loss carryforward	Indefinite	Indefinite, $3,000/yr against ordinary income

Exemptions and Reliefs That Save Real Money

Exemption / Relief	Effect	Key Conditions
Principal Private Residence (PPR)	100% exempt	Must be your main home; final 9 months always exempt
ISA gains	100% exempt	Must stay within the ISA wrapper
Pension gains (SIPP, workplace)	100% exempt	Tax applied on withdrawal as income, not capital
Spouse / civil partner transfer	No gain or loss	Must be living together in the tax year
Business Asset Disposal Relief	18% flat from Apr 2026	Qualifying business, 5% shareholding for 24 months, £1M lifetime
Gift Hold-Over Relief	Defers gain to recipient	Qualifying business assets or trust transfers
Enterprise Investment Scheme (EIS)	Defers gain until EIS shares sold; tax-free after 3 years	Reinvest within 1 year before or 3 years after disposal
Bed and ISA / Bed and SIPP	Resets cost base	Sell and rebuy inside wrapper to shelter future growth

CGT on Property: The 60-Day Rule

UK residents disposing of residential property that is not their main home must report the gain and pay CGT within 60 days of completion, using HMRC's online CGT on UK Property service. This is separate from and earlier than the main Self Assessment deadline (31 January after the tax year end). Missing the 60-day deadline triggers an automatic £100 penalty, plus daily and monthly penalties for continued default. Non-UK residents must report every UK property disposal within 60 days, even when no tax is due.

Chargeable property disposals include:

• Buy-to-let investment properties
• Second homes and holiday lets
• Inherited property that was never your main residence
• Property used partly for business (mixed-use)
• Land separated from your main home's garden (over 0.5 hectares)

How Much Does the UK Raise from CGT?

HMRC's CGT statistics show receipts of £13.1 billion in 2024/25, down from the record £16.9 billion in 2022/23 because the 2022/23 rush of disposals (before the AEA was first cut) pulled gains forward. The Office for Budget Responsibility forecasts CGT receipts of £20.3 billion in 2025/26 as the 18%/24% rates and lower AEA work through the system. Around 378,000 taxpayers reported a gain in 2023/24 per HMRC - roughly 0.6% of UK adults - yet CGT now raises more than inheritance tax (£8.4bn in 2024/25 per the same HMRC bulletin).

The top 1% of CGT payers report around 62% of all gains, so the tax is highly concentrated at the top of the distribution. This matters for anyone selling a business or a large share portfolio, because even a modest rate rise compounds into a large bill.

Common Mistakes That Cost Money

• Forgetting the 60-day property reporting deadline. The £100 auto-penalty applies even if the gain is under the AEA. Always report, even if no tax is due.
• Selling into the 24% band by accident. A bonus or second job can push your income over £50,270, dragging gains from 18% to 24%. Check timing against the UK income tax calculator before disposing.
• Not using the spouse exemption. Transfers between married or civil partner couples are no gain / no loss. Moving an asset before sale effectively doubles the AEA (£6,000) and can use both basic rate bands.
• Selling all holdings in one tax year. £6,000 spread over two tax years is tax-free. £6,000 in one year creates £3,000 of taxable gain.
• Ignoring Bed and ISA. You can crystallise a gain within the AEA, rebuy inside an ISA, and all future growth is CGT-free.
• Missing BADR qualifying conditions. Since October 2024 the holding period is 24 months, and you must hold 5% of ordinary shares and voting rights. Selling at 23 months costs a full-rate bill.
• Forgetting capital losses. Losses must be claimed within 4 years. Once claimed, they carry forward indefinitely against future gains.

Tax-Efficient Strategies for Big Gains

When a gain is too large for the AEA, staging and sheltering work together. A typical pattern for a £50,000 unrealised gain on a shares holding:

1. Sell £3,000 worth of gain this tax year (tax-free via AEA).
2. Transfer half of the remaining holding to a spouse at the same base cost.
3. Each spouse sells £3,000 worth next tax year (£6,000 combined tax-free).
4. Use both spouses' £20,000 ISA allowances to Bed and ISA the proceeds so future growth is sheltered.

If you are also building long-term wealth across multiple assets, the net worth calculator gives a single view of your position before and after CGT.

This tool estimates CGT using the 2026/27 HMRC rules. It does not cover non-resident rules in detail, trusts, partnerships, carried interest, or chattel exemptions. Always cross-check with HMRC guidance or a qualified tax adviser. All calculations run in your browser - no data is sent to any server.

Sources

• GOV.UK - Capital Gains Tax rates and allowances
• GOV.UK - Changes to the rates of Capital Gains Tax (Autumn Budget 2024 Tax Information Note)
• HMRC - Capital Gains Tax statistics commentary
• GOV.UK - Report and pay Capital Gains Tax (60-day property deadline)
• GOV.UK - Business Asset Disposal Relief
• Office for Budget Responsibility - Capital Gains Tax forecasts
• IRS - Topic 409, Capital Gains and Losses