Capital Gains Tax on shares and crypto — the rules, the rates and the 30-day trap

Capital Gains Tax used to be something most retail UK investors didn’t encounter — the annual exempt amount was £12,300 until 2023, easily covering most ordinary gains. Two successive cuts brought it down to £3,000 from April 2024, and a much bigger slice of savers now have a real CGT liability to manage.

This is the practical version for someone holding shares, ETFs, funds or cryptocurrency outside a tax-favoured wrapper.

The basic mechanics

CGT applies when you dispose of an asset for more than its acquisition cost (plus allowable costs). The taxable amount is the gain — not the proceeds — and only the portion above the annual exempt amount is taxed.

A simple example: bought £4,000 of a share, sold for £7,000. Gain: £3,000. With the £3,000 annual exempt amount, no tax due — perfectly within the allowance.

Same purchase, sold for £10,000. Gain: £6,000. Less £3,000 exempt amount: £3,000 taxable. At 18% (basic-rate) or 24% (higher-rate) the tax is £540 or £720 respectively.

The October 2024 Budget changed the CGT rates for non-property assets:

• Basic-rate taxpayer: 18% on gains (up from 10%).
• Higher-rate / additional-rate taxpayer: 24% on gains (up from 20%).

Residential property gains have different (slightly higher) rates — see our buy-to-let tax guide.

Allowable costs

When calculating gains, you can deduct:

• The original purchase cost.
• Transaction costs to buy (broker fees, stamp duty on shares).
• Transaction costs to sell.
• Any “enhancement expenditure” that adds to the asset’s value (rare for shares; common for property).

For shares and crypto, the deductibles are usually just the purchase cost plus broker / exchange fees. Keep records of everything — HMRC can ask for evidence going back many years.

How the basic-rate vs higher-rate split works

You don’t pay one rate on the whole gain. Instead:

1. Calculate your taxable income (after personal allowance and pension contributions) for the tax year.
2. Add the taxable gain to that figure.
3. Any portion of the gain that sits within the basic-rate band is taxed at 18%.
4. Any portion above is taxed at 24%.

A worked example. Income of £35,000 (after PA, £22,430 taxable). Basic-rate band tops at £50,270, leaving £14,840 of basic-rate band unused.

Gain of £25,000 minus £3,000 exempt amount = £22,000 taxable.

• £14,840 of gain at 18% = £2,671.
• £7,160 of gain at 24% = £1,718.
• Total CGT: £4,389.

If the same person had been earning £55,000, all £22,000 of gain would be at 24% = £5,280.

The income-stacking rule means timing gains for a tax year with lower income (a sabbatical year, a low-pay year, the year before starting a new high-paid job) can save tax. Higher-income years are more expensive.

The 30-day rule for shares (the “same-day” and “bed-and-breakfast” rules)

You can’t crystallise a gain on Monday and rebuy the same shares on Tuesday to refresh the cost basis. The 30-day rule prevents this:

1. Same-day matching: if you buy and sell the same security on the same day, the sell is matched to that day’s buy for CGT purposes — not to your historical holding.
2. 30-day rule (bed-and-breakfasting prohibition): if you sell a security and rebuy the same security within 30 days, the rebuy is matched against the sale for CGT purposes. The sale doesn’t crystallise a gain against your older holding.

So “sell on Monday, rebuy on Tuesday” doesn’t work. You either need to wait at least 31 days to rebuy, or use one of the workarounds:

• Bed-and-ISA: sell in your general account, rebuy in your ISA. The ISA buy isn’t the same beneficial ownership for the 30-day rule. Allowance permitting. See our bed-and-ISA guide.
• Bed-and-spouse: sell in your general account, your spouse rebuys in their general account. Different beneficial owner — the 30-day rule doesn’t apply between spouses.
• Bed-and-SIPP: sell in your general account, rebuy in your SIPP. Same allowance / annual contribution constraints apply.
• Bed-and-similar: sell one ETF tracking the FTSE 100, buy a different ETF tracking the FTSE 100 from a different provider. Different securities; the 30-day rule doesn’t apply.

The 30-day rule is enforced — HMRC can pick it up via broker reporting. Don’t try to skirt it.

How CGT works for crypto

HMRC treats cryptocurrency as property for CGT purposes. Same mechanics as shares:

• Each disposal is a taxable event.
• Gain = proceeds minus acquisition cost.
• £3,000 annual exempt amount.
• Same 18%/24% rates split based on income.

The key thing that catches crypto holders out: disposal includes many activities that don’t feel like “selling” to the holder:

• Selling crypto for GBP.
• Selling one crypto for another (e.g. BTC for ETH). Both sides are disposals; you have a gain on the BTC you sold.
• Using crypto to pay for goods or services. This is a disposal of the crypto at the GBP value at the time.
• Gifting crypto to anyone other than your spouse. This is a disposal at market value.

Crypto-to-crypto transactions are the biggest source of accidental tax liability. A trader making 100 swaps in a year between different tokens has 100 disposals to calculate, even if they never converted back to GBP.

HMRC also uses pooling rules for crypto, similar to shares — your entire holding of a specific token is treated as one pool with an average acquisition cost, not as separate tranches.

For more on the practical mechanics of crypto reporting, see our crypto gains declaration guide.

Reporting and payment

Two routes for reporting:

1. Self-assessment. Include gains and losses in the SA return for the tax year, file by 31 January after year-end, pay any CGT due by the same date. This is the route for most share / fund / crypto investors.

2. Real-time CGT service. HMRC’s online service lets you report and pay gains during the year without waiting for the SA return. Optional for most people; useful if you want to clear the obligation quickly or if you don’t otherwise file SA.

Residential property gains have a separate, mandatory 60-day reporting and payment deadline — see the buy-to-let guide. Shares and crypto don’t have this; the normal SA timetable applies.

The reporting threshold

You need to report capital gains to HMRC if either of these is true:

• Your total taxable gains exceed the annual exempt amount (£3,000 currently).
• Your total proceeds from disposals exceed 4× the AEA (currently £12,000).

The second test catches people who’ve had large sell-and-rebuy activity even if the net gains were small. The total proceeds figure is the gross amount you sold, not the gain.

So if you sold £20,000 of shares and rebought £18,000 of different shares, with a £500 net gain, you’re below the gain threshold but above the proceeds threshold — you still need to report.

Loss relief

Losses can be offset against gains in the same tax year first, with any excess carried forward indefinitely against future gains.

To use a carried-forward loss, you have to register the loss with HMRC within four years of the end of the tax year in which it occurred. Either report it on a self-assessment return for that year, or write to HMRC separately.

A registered loss from 2020/21 is still usable against gains in 2026/27. An unregistered 2020/21 loss is gone forever after 5 April 2025 — the four-year deadline has passed.

Crypto losses can be offset against crypto gains, but also against other CGT gains (shares, property). They’re not ring-fenced.

The wrapper strategies

Inside an ISA or SIPP, there’s no CGT. Disposals don’t create taxable events, the £3,000 AEA isn’t consumed, and you don’t need to report anything.

This is the primary reason for holding equity investments inside ISAs and SIPPs rather than general accounts — the tax administration burden disappears entirely.

For investors hitting the £20,000 ISA limit and still wanting to invest more, the general account becomes necessary — but the £3,000 AEA, the 18%/24% rates and the reporting obligations all kick in. Bed-and-ISA each tax year is one of the most common ways of managing this drift over time.

Specific patterns to plan around

• Use the AEA each year if you have non-ISA holdings. £3,000 of gains crystallised tax-free annually is £15,000 over 5 years. Use it or lose it; it doesn’t carry forward.
• Plan disposals across tax years if a gain would exceed the AEA. Sell half this year, half next year — sometimes useful, sometimes administratively pointless depending on the amount.
• Crystallise losses before 5 April to bring them into the current year for offset against current-year gains.
• Coordinate with a spouse’s CGT position. Inter-spouse transfers are tax-neutral (no CGT triggered), so cost basis can be moved before disposal to make use of both AEAs and both basic-rate bands.
• Don’t forget pension contributions. Pension contributions reduce taxable income, which can push the basic-rate band ceiling higher and reduce how much of a gain is taxed at the higher 24% rate.

When you don’t owe CGT

A few common situations where the gain is exempt:

• Inside an ISA or pension wrapper.
• Gains within your £3,000 AEA for the year.
• Gifts to your spouse or civil partner — tax-neutral transfer.
• Gilt (UK government bond) gains — gilts are CGT-exempt.
• Personal possessions worth under £6,000 — chattels rules.
• Your main residence under Principal Private Residence relief (though crypto and shares are obviously not relevant here).

The bigger picture

The shrinking AEA and the rising CGT rates have made tax planning materially more important for UK investors with non-ISA holdings. The fundamentals are unchanged: use the wrappers where you can, use the AEA each year, register losses promptly, plan disposals around income years.

For most ordinary investors, the simplest approach is to keep new contributions inside ISAs and SIPPs as a first priority, and bed-and-ISA existing general account holdings each year to drift them into wrapper-protected territory over time.

For the related bed-and-ISA mechanics, see our bed-and-ISA explained guide. For crypto-specific reporting, see how to declare crypto gains to HMRC.

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Last updated 1 June 2026. This guide is educational and is not personal financial advice. CGT rules, rates and allowances are set by HMRC and can change in any Budget — verify current figures on gov.uk before relying on them. See our disclaimer.