UK CGT Calculator 2026/27: Gains, Losses & Allowance

A UK Capital Gains Tax calculator is a useful first pass when you are deciding whether a sale, transfer or exchange could create a taxable gain. It is not a simple sale-price calculator. The result depends on the asset, acquisition history, allowable costs, disposal date, taxable income, losses, reliefs and whether the asset is held alone or jointly.

Use the CGT Calculator→ to model proceeds, original cost, allowable expenses, income and losses for 2026/27. The calculator can show an estimated gain, the part covered by the annual exempt amount and an illustrative tax bill. It cannot decide whether an asset is exempt, confirm a market-value disposal, apply every matching rule or submit a return to HMRC.

For 2026/27, GOV.UK lists an individual annual exempt amount of £3,000. Most individual chargeable gains are taxed at 18% or 24%, depending on where the gain falls relative to the Income Tax basic-rate band. Those figures are inputs to a scenario, not permission to treat every asset or transaction as identical.

What a UK CGT calculator is estimating

The starting point is the gain on each disposal:

Gain = disposal proceeds − acquisition cost − allowable disposal costs − allowable improvement costs

That formula is deliberately simplified. A disposal can be a sale, gift, exchange or another event where you stop owning an asset. If there is no cash price, market value may be relevant. The acquisition cost may include more than the original invoice, and the allowable-cost test depends on the asset and the expense. A routine repair is not automatically a capital improvement; a dealing fee or legal cost is not automatically allowable in every context.

The calculator then combines the relevant gains and losses, applies any relief assumption, deducts the annual exempt amount where appropriate, and considers how the taxable gain sits alongside your income. It should not be used to conceal a missing transaction. Entering only the profitable sale while leaving out a same-year loss, an earlier disposal or a jointly owned share can produce a misleading result.

The tax year matters. The UK tax year runs from 6 April to the following 5 April. A disposal on 5 April and a disposal on 6 April can therefore use different annual exemptions and rates. Record the legally relevant disposal date, not merely the date you began negotiating or received a valuation.

Step 1: choose the asset and disposal type

Start by classifying the asset before entering numbers. The same arithmetic cannot safely be applied to every disposal.

Assets held inside an ISA or pension normally sit outside the ordinary CGT calculation, but do not assume an account label solves every question. A disposal of a taxable investment account, a transfer to another person and a withdrawal from a wrapper are different events. If the asset is a business interest, a trust asset, an overseas asset or part of a connected-party arrangement, use the calculator as an organising tool and obtain a more specific review.

Step 2: enter proceeds and the acquisition history

Enter the amount received or the best-supported market value at disposal. Then enter the acquisition cost for the units or property being disposed of. If there were several purchases, do not choose whichever purchase gives the most favourable answer. Use the matching rules that apply to the asset.

Keep an evidence file containing:

• purchase contracts, dealing confirmations and completion statements;
• the dates and number of shares, units or tokens acquired;
• the sale contract, settlement statement and disposal date;
• stamp duty, transaction fees, legal fees and other potentially allowable costs;
• invoices for capital improvements rather than routine maintenance;
• valuations where an asset was gifted, exchanged or transferred without an ordinary price; and
• records showing whether the asset was held in an ISA, pension, trust or business structure.

For a property, the purchase price is only one part of the history. Acquisition tax and professional costs may matter, while the treatment of improvements depends on whether they enhance the asset and remain reflected in it at disposal. For investments, reinvested dividends, fund distributions and corporate actions can change the cost record. For cryptoassets, a spreadsheet that records only cash withdrawals is not enough because an exchange of one token for another can itself be a disposal.

Step 3: subtract allowable costs carefully

The calculator has a field for allowable costs because the gain is not simply sale price minus purchase price. Enter costs that are directly connected with buying, selling or enhancing the asset and that are permitted by the relevant rule. Keep the description beside the number so the calculation can be reviewed later.

Do not use costs twice. If a solicitor's fee was already included in the acquisition cost, do not add it again as a separate expense. Do not enter mortgage interest, ordinary household bills or routine repairs as capital improvement costs just because they were expensive. When a property was partly a home and partly let, the expense and relief analysis may need an allocation rather than one unrestricted deduction.

If the disposal is a gift or transfer, there may be no cash proceeds to type into a bank-style calculator. A market-value assumption may be needed, and the right answer can depend on the relationship between the parties. Add a note to the result rather than presenting a market-value estimate as an observed sale price.

Step 4: apply losses in the right order

Losses are a major reason a calculator result differs from a headline gain. GOV.UK explains that allowable losses can reduce gains in the same tax year. Unused losses can generally be carried forward, but they must be claimed through the applicable HMRC process and the evidence must be retained.

Enter separately:

1. losses arising from disposals in the current tax year;
2. losses brought forward from earlier tax years; and
3. any loss already used against another gain or previously claimed.

Do not enter a paper loss on an asset that has not been disposed of. A fall in a fund's value is not the same as a realised loss. Also check share matching rules before treating a sale and repurchase as a clean loss: a repurchase within the relevant period can affect which acquisition is matched and the cost attributed to the holding.

GOV.UK says a capital loss can generally be claimed up to four years after the end of the tax year in which the disposal occurred. That time limit is a claim rule, not a reason to omit the loss from a current calculation. Record the disposal, the calculation and the route used to notify HMRC. Connected-person disposals can have special restrictions, so do not assume a loss to a family member has the same result as an arm's-length sale.

Step 5: understand the £3,000 annual exempt amount

For 2026/27, the GOV.UK CGT rates page lists an annual exempt amount of £3,000 for individuals. The exemption is applied to the person's relevant annual gains after the gain and loss position is considered. It is not £3,000 per asset, per account or per sale, and it is not a percentage reduction.

This example does not establish the final CGT because income, asset type, reliefs and the disposal date still matter. It does show why entering a £28,000 gain and manually subtracting £3,000 without recording losses can produce the wrong audit trail.

Unused annual exemption is not a carried-forward loss. If you make no disposal in a tax year, you cannot normally bank the £3,000 for a later year. A spouse or civil partner has a separate tax position and separate annual exemption, but you must not combine two allowances automatically unless the ownership and transfer facts support that planning.

Step 6: let income determine the rate split

Most individual gains in 2026/27 are charged at 18% or 24%. The rate is not selected solely by choosing “basic-rate taxpayer” in a form. Add taxable income and the taxable gain conceptually to identify how much of the gain falls within the basic-rate band and how much is above it. The calculator therefore asks for income or an equivalent rate-band assumption.

For example, assume an individual has a £21,000 chargeable gain after losses and the annual exempt amount. If £8,000 of that gain fits within the person's remaining basic-rate band, the illustrative tax is:

If the person has different income, the split changes. If the disposal qualifies for a specific relief, a separate rate or limit may apply. The calculator's result should therefore show the assumptions beside the number. Never present a single percentage as though it applied to the whole household or every asset.

Shares: matching rules before the calculator result

Shares are one of the most common reasons a basic calculator is incomplete. When you sell shares and buy the same class again, HMRC matching rules can apply in a priority order. Same-day acquisitions and acquisitions in the following 30 days can be matched before the remaining shares enter or leave the Section 104 pool. The pool uses an averaged allowable cost rather than a hand-picked parcel.

Use the Capital Gains on Shares 2026/27 guide for the detailed workflow. In the calculator, enter a reliable matched cost, not simply the oldest purchase price. If you are using a bed-and-ISA strategy, model the taxable disposal and the ISA purchase as distinct account events and retain the dealing confirmations.

Property: relief and the 60-day boundary

Property gains need extra care. A main residence may qualify for Private Residence Relief for some or all of the gain, but the answer can change with periods of letting, business use, multiple homes, ownership changes or residence status. A buy-to-let or second home should not be entered as “property” and assumed to receive the same treatment as a main home.

The Capital Gains Tax on Property 2026/27 guide covers the asset-specific questions. For a UK-resident individual who has CGT to pay on a UK residential-property disposal, GOV.UK requires the gain to be reported and paid through the property service within 60 days of completion. Non-UK residents have broader reporting duties for UK property and land. The 60-day statement is therefore a qualified reporting rule, not a universal deadline for every property calculation.

Before relying on the result, record completion, occupation, ownership, letting and improvement dates. If a property is jointly owned, calculate each person's share and each person's income, losses and exemption separately. A household total is useful for planning but is not a substitute for the individual computations.

Joint ownership, spouses and civil partners

Joint ownership does not create one shared CGT taxpayer. Normally, each beneficial owner has a share of the gain, a separate annual exempt amount and a separate income position. Enter the ownership percentage and confirm it is the beneficial ownership rather than relying only on the name shown on an account or title.

Transfers between spouses or civil partners can have no-gain/no-loss treatment in the circumstances covered by the rules. That can allow a couple to organise ownership before a later disposal, but it does not make every family transfer exempt. A transfer to an adult child, sibling or friend can be a disposal and may need market value. A transfer involving a company or trust can create further complications.

Use the calculator to compare each person's position, then document the transfer and ownership facts. Do not type both people's gains into one person merely to use one combined tax-band selection.

Cryptoassets and other non-standard disposals

Cryptoasset calculations need a transaction ledger rather than one annual sale figure. Selling for pounds, exchanging one token for another or using a token to pay for something can be a disposal. Mining, staking, employment rewards and some airdrops can have income-tax implications before a later disposal creates a CGT calculation.

Link the calculator result to the Cryptoasset Tax guide and retain wallet exports, exchange statements, sterling valuations, fees and transaction identifiers. A cost basis imported from a platform may omit transfers between wallets or assets held with another provider. If the calculator cannot reconcile the acquisition history, its result is incomplete even if the final number looks precise.

Reporting, payment and records

GOV.UK's reporting guidance asks taxpayers to work from the transaction facts and use the applicable service or return. A calculator cannot decide whether you must use Self Assessment, the UK property service, a non-resident route or another HMRC process. It also cannot determine whether a gain is reportable when a relief, trust, business or residence issue changes the facts.

After the estimate, prepare a short evidence pack:

• the disposal date and asset description;
• proceeds or supported market value;
• acquisition cost and matching calculation;
• allowable costs and improvement invoices;
• current-year and brought-forward losses;
• relief conditions and supporting records;
• taxable income used for the rate split; and
• the HMRC route and deadline that applies to the completed facts.

For a residential-property disposal, check the 60-day requirement as soon as completion is known. For other disposals, do not infer a deadline from the property rule. Check the applicable GOV.UK service, Self Assessment instructions and any notice from HMRC. Keep the calculator output with the underlying records so a later change in price, cost, loss or relief can be traced.

Common questions

Run the CGT Calculator→ with one documented disposal scenario at a time. For asset-specific detail, continue to Capital Gains Tax 2026/27, Capital Gains on Shares 2026/27, Capital Gains Tax on Property 2026/27 and Cryptoasset Tax 2026/27.

Official sources

• GOV.UK — Capital Gains Tax rates
• GOV.UK — If you make a loss
• GOV.UK — Reporting and paying Capital Gains Tax
• GOV.UK — Capital Gains Tax

This guide is educational. It does not determine your tax residence, confirm relief eligibility, replace HMRC's calculation or provide financial or tax advice.