UK Capital Gains Tax Calculator

Selling a second home, a buy-to-let property, or a chunk of shares can trigger a tax bill many people do not see coming, since the profit you make is treated very differently from your regular income. Capital Gains Tax is charged on the gain itself, not on the full sale price, but working out the exact figure takes a few steps.

This calculator works through those steps for you, from your raw gain down to the tax actually owed, after your annual exempt amount and the correct rate for your circumstances. It is worth running the numbers well before you sell, since with enough notice there are sometimes legitimate ways to reduce a Capital Gains Tax bill, such as timing a sale across two tax years or making use of allowances available to a spouse or civil partner.

How to use the Capital Gains Tax calculator

Enter the price you sold the asset for, the price you originally paid, and any allowable costs, such as agent fees or legal costs, on either side of the transaction. Choose whether the asset is property or something else, and whether you are a higher or additional rate taxpayer. The calculator works out your gain, applies your annual exempt amount, and shows the tax owed.

How the calculation works

Your gain is simply your sale price, minus your original purchase price, minus any allowable costs along the way. The first £3,000 of gains each tax year is completely tax free, thanks to the annual exempt amount. Anything above that is taxed at 18% if you are a basic rate taxpayer, or 24% if you are a higher or additional rate taxpayer.

Since the October 2024 Budget, these two rates apply equally to residential property that is not your main home and to other chargeable assets like shares, which simplified a system that previously used different rates for each. This calculator uses the current unified rates for both asset types.

Worked example

Say you sell a rental property for £350,000, having bought it for £250,000, with £5,000 of allowable costs such as agent and legal fees on the sale. Your gain is £95,000.

After the £3,000 annual exempt amount, £92,000 is taxable. As a higher rate taxpayer, that is taxed at 24%, giving a Capital Gains Tax bill of around £22,080. As a basic rate taxpayer instead, the same £92,000 taxed at 18% would come to around £16,560, a difference of over £5,500 depending purely on which tax band applies to you.

Married couples and civil partners

Transfers of assets between spouses and civil partners are generally exempt from Capital Gains Tax, which opens up a genuinely useful piece of planning for couples who jointly own an asset that is about to be sold. By holding an asset jointly, or transferring a share to a spouse before selling, a couple can potentially use two annual exempt amounts instead of one, and may be able to spread the gain across two sets of tax bands depending on each partner's other income. This only applies to legally married couples and registered civil partners, not to unmarried couples living together.

Common mistakes to avoid

A common mistake is assuming your main home is covered by the same rules as a second property. In almost all cases, Private Residence Relief means no Capital Gains Tax is due at all when you sell the home you actually live in, so this calculator is not the right tool for that situation. Another mistake is forgetting the 60 day reporting deadline for UK residential property that is not your main home. Missing it can lead to penalties even if you eventually pay the correct tax owed.

It is also easy to underestimate allowable costs. Genuine costs of buying and selling, including legal fees, agent fees, and in some cases the cost of improvements made to the property, can all reduce your taxable gain, so it is worth gathering the relevant paperwork before finalising your figures.

Finally, do not forget losses. If you have made a loss on another asset in the same or a previous tax year, you may be able to offset it against a gain, reducing your taxable amount further. Losses generally need to be reported to HMRC to be used later, even in a year where you have no gains to offset them against, so keeping a record as you go is worthwhile.

Related calculators

If the sale relates to a property purchase you are also planning, our stamp duty guide and stamp duty calculator cover the tax due on the buying side. For the rest of your tax position, our Income Tax calculator and dividend tax calculator cover salary and dividend income, and our mortgage calculator can help if you are buying another property with the proceeds.