Capital Gains Tax Calculator (UK)

UK Capital Gains Tax Guide

What do I need to know about CGT Rates for 2026/27?

For shares and most assets: basic rate taxpayers pay 10%, higher/additional rate taxpayers pay 20%. For residential property (not your main home): basic rate 18%, higher rate 24% from October 2024. The annual CGT allowance for 2026/27 is £3,000 — only gains above this are taxed. This was cut from £12,300 in 2022/23 as part of HMRC's ongoing reduction of the allowance.

What Counts as a Gain?

Your gain is sale proceeds minus original cost, minus any allowable costs. Allowable deductions include: purchase costs (stamp duty, legal fees), improvement costs (for property, not maintenance), and selling costs (estate agent fees, legal fees). For shares, you can also offset losses from other CGT assets in the same tax year.

What do I need to know about Main Residence Relief?

Your primary home (Principal Private Residence) is fully exempt from CGT. If you have two properties, only one can be your PPR at any time. Letting relief applies if you have rented out a property that was previously your main home. HMRC can investigate disposals going back several years if they suspect under-reporting.

What should I know about Reducing Your CGT Bill?

Use your annual exempt allowance every tax year — it cannot be carried forward. Transfer assets to a spouse before selling to use both allowances. Hold shares in an ISA where gains are fully exempt. Offset capital losses against gains in the same or future tax years. Consider the timing of the sale — selling in a year when your income is lower may reduce the rate applied.

What do I need to know about Using Losses to Reduce CGT?

Capital losses on other assets sold in the same tax year must first be used to offset gains before the annual tax-free allowance is applied, and any unused losses can be carried forward indefinitely to offset gains in future tax years — though they must be reported to HMRC, generally within four years of the loss, to be usable later. This means it's worth reviewing your full portfolio before the end of the tax year: if you're sitting on both a large gain and a separate loss-making holding you were planning to sell anyway, realising both in the same tax year can meaningfully reduce the CGT bill on the gain. Be aware of the 'bed and breakfasting' rule — selling a holding to crystallise a loss (or use the allowance) and then buying the identical shares back within 30 days means the loss is disallowed for tax purposes, though this can sometimes be worked around by buying the equivalent fund within an ISA or pension instead, or by having a spouse repurchase the shares.

What's the key thing to understand about Transferring Assets to a Spouse or Civil Partner?

Transfers of assets between spouses or civil partners are exempt from Capital Gains Tax regardless of the gain involved, which makes 'inter-spouse transfer' one of the most widely used legitimate CGT planning tools. If one partner has used up their annual CGT allowance (or pays tax at a higher marginal rate) and the other hasn't, transferring part of an asset — shares, a second property, or a business holding — to the lower-rate or unused-allowance spouse before a sale can let a couple use two tax-free allowances and benefit from the lower-rate partner's tax band on the gain. The transfer itself must be a genuine, unconditional gift of beneficial ownership (not just on paper) to be effective, and for jointly-held assets like a buy-to-let property, the split of ownership can be adjusted via a formal declaration. This only works for legally married couples or registered civil partners — it does not apply to unmarried cohabiting partners, who have no equivalent exemption for gifts between them.

Why Your Main Home Is Usually Exempt, But Not Automatically in Every Case

In the UK, Private Residence Relief generally exempts gains on the sale of your main home from Capital Gains Tax entirely, which is why most people never think of CGT in connection with selling their own house. However, this relief can be reduced or lost in part if the property wasn't your only or main residence throughout the full period of ownership — for example, periods it was let out to tenants, used partly as a business, or simply not lived in for an extended stretch — in which case a proportion of the gain corresponding to that non-qualifying period can become taxable. This is a common trap for anyone who has rented out a former home at some point, or owned more than one property and not clearly nominated which was their main residence for tax purposes.

Why the Annual Exempt Amount Resets Each Year and Rewards Spreading Disposals

Capital Gains Tax includes an annual tax-free allowance (the Annual Exempt Amount) that resets each tax year and cannot be carried forward if unused — meaning a gain realized just before the tax year-end and a similar gain realized just after it can be taxed very differently depending purely on which side of the deadline they fall, since each tax year gets its own fresh allowance. Investors or property owners planning to dispose of multiple assets with gains sometimes deliberately spread disposals across different tax years specifically to use more than one year's allowance, rather than realizing all the gains within a single tax year and using only one allowance against the combined total.

Worked Example: CGT on a Share Sale After the Annual Exemption

An investor sells shares for £25,000 that originally cost £10,000, a gain of £15,000. The UK's tax-free annual exempt amount is currently £3,000 (reduced in stages from £12,300 a few years ago), so the taxable gain is £15,000 − £3,000 = £12,000. For a basic-rate taxpayer whose gain fits inside their remaining basic-rate band, the tax is £12,000 × 18% = £2,160. For a higher-rate taxpayer, the same taxable gain is charged at 24%: £12,000 × 0.24 = £2,880.

Note that share and 'other asset' CGT rates were raised to match residential property rates (18%/24%) from the October 2024 Budget onward, closing a gap that previously made shares cheaper to dispose of than a second property — always confirm the exact current-year rates on gov.uk, since CGT rates and reliefs have changed more than once in recent Budgets.

How CGT Interacts With Self Assessment and Payment Deadlines

Most UK capital gains must be reported and paid through Self Assessment by the usual 31 January deadline following the tax year of disposal, though gains on UK residential property have a separate, much tighter window — currently typically 60 days from completion — reported and paid online even if you don't normally file a tax return. Missing either deadline can trigger penalties and interest in the same way as late Income Tax payment, so it's worth treating a property sale's CGT obligation as a near-term task rather than something to leave until the following January. If your only gains are from shares or funds held in an ISA, there's nothing to report at all, since gains inside an ISA are always tax-free — which is one reason many investors prioritise using their ISA allowance before investing in a general account.

Carrying Forward Unused Losses to Future Tax Years

A capital loss that isn't needed to offset gains in the same tax year doesn't disappear — it can usually be registered with HMRC and carried forward indefinitely to offset gains in any future year. This matters for anyone who sold an underperforming investment at a loss: reporting that loss on a tax return, even in a year with no gains to set it against, preserves the right to use it later. Losses must typically be used against gains in the same year first before any carry-forward amount can be applied, and losses can't usually be carried back to an earlier year except in limited circumstances such as death. Keeping a simple running log of unused losses, with the dates and amounts, avoids losing track of a valuable offset that might not be used for several years.