How Are Investments Taxed?

Capital Gains Tax — The Basics

When you sell an investment for more than you paid for it, the profit is a capital gain, and in the UK that gain is potentially subject to Capital Gains Tax (CGT). This applies to shares, funds, investment trusts, and most other investments held outside a tax-advantaged wrapper — it does not apply to your main home, most personal possessions, or, crucially, to anything held inside an ISA or pension.

Every UK taxpayer gets an annual exempt amount — a slice of gains each tax year that is entirely tax-free, regardless of income. At time of writing, that annual exempt amount is £3,000, having been reduced sharply in recent years from £12,300 in the 2022/23 tax year, down to £6,000 in 2023/24, and down again to £3,000 from the 2024/25 tax year onward. This repeated reduction is itself an important lesson: CGT allowances and rates in the UK have changed significantly and repeatedly in just the last few years, and anyone making investment decisions based on a specific number should treat it as provisional and check HMRC's current published rates before relying on it for anything significant.

Which rate applies — 18% or 24% — depends on your total taxable income for the year, including the gain itself in the calculation: gains are effectively stacked on top of your other income, and the portion that falls above the basic rate threshold is taxed at the higher 24% rate, even if the rest falls within the lower band. This means a large one-off gain can push you into paying the higher CGT rate on part of it, even if your regular salary alone would keep you as a basic rate taxpayer.

Working Through a Real Calculation

Suppose you bought shares for £15,000 several years ago, and sell them this tax year for £24,000 — a gain of £9,000. You have made no other disposals this tax year, so the full £3,000 annual exempt amount is available. The taxable gain is £9,000 − £3,000 = £6,000.

If your other taxable income for the year is £35,000 (comfortably within the basic rate band, which runs up to £50,270 at time of writing), the entire £6,000 taxable gain falls within the basic rate band too, and is taxed at 18%: a CGT bill of £1,080. If instead your other income is £48,000, only £2,270 of the gain fits within the remaining basic rate band (taxed at 18%, or £408.60), and the remaining £3,730 of the gain is taxed at 24% (£895.20) — a total bill of £1,303.80, higher than the first scenario purely because of where the gain fell relative to the rate band threshold, with an identical underlying gain.

This stacking effect is the single most common source of confusion in CGT calculations, and it is worth the extra care, because it means the tax rate on a gain is not a fixed property of the investment — it depends entirely on your total income picture for that specific tax year, which is also why timing a large disposal (selling in a lower-income year, for instance, around a career break or after retirement) can make a genuine difference to the final tax bill.

Dividend Tax — A Separate System, Same Logic

Dividends are taxed under a completely separate set of rules and rates from capital gains, even though both arise from the same investment. The dividend allowance — the amount of dividend income that is tax-free each year regardless of your other income — stands at £500 at time of writing, having also been reduced substantially in recent years from £2,000 in 2022/23, following a similar trajectory to the CGT allowance.

Dividend income above the allowance is taxed at rates tied to your income tax band: 8.75% for basic rate taxpayers, 33.75% for higher rate taxpayers, and 39.35% for additional rate taxpayers — all noticeably lower than the equivalent income tax rates on salary, which is a deliberate policy choice reflecting that dividends are paid out of profits that have already been taxed once at the corporate level. Inside an ISA or pension, dividend income is entirely tax-free regardless of amount, which is a major, often underappreciated reason to prioritise ISA contributions specifically for income-focused or dividend-paying investments.

This is also why the order in which you build an investment portfolio across accounts matters more than many people realise: an income-focused portfolio generating £3,000 a year in dividends sitting in a general investment account could trigger a real, recurring annual tax bill once it exceeds the £500 allowance, while the exact same portfolio inside an ISA generates that income completely tax-free, every single year, indefinitely.

The ISA Wrapper, Properly Understood

A Stocks and Shares ISA is not an investment itself — it is a tax wrapper you put investments inside. Once a share, fund, or bond sits within the ISA, all capital gains, dividends, and interest it generates are permanently tax-free, for as long as you hold it inside the wrapper, with no need to report anything to HMRC related to it.

The UK's total annual ISA allowance (across Cash ISAs, Stocks and Shares ISAs, Lifetime ISAs, and Innovative Finance ISAs combined) is £20,000 per person at time of writing, and this allowance resets every 6 April with the new tax year — unused allowance does not carry forward, which is why "use it or lose it" genuinely applies here. A couple can therefore shelter up to £40,000 a year between them using their individual allowances.

The practical implication for tax planning is straightforward: for the vast majority of UK retail investors, whose total portfolio is well under the amounts where CGT and dividend tax become a meaningful annual drag, maximising ISA contributions before using a general investment account at all removes the tax question almost entirely, for as long as the money stays inside the wrapper.

The Pension Wrapper — A Different Trade-off

A Self-Invested Personal Pension (SIPP) or workplace pension offers a different, in some ways more powerful, tax advantage: contributions themselves receive tax relief at your marginal income tax rate (so a basic rate taxpayer contributing £800 has it topped up to £1,000 automatically, with higher and additional rate taxpayers able to claim further relief through their tax return), and all growth inside the pension — capital gains and dividends alike — is tax-free while it remains invested.

The trade-off is access: pension money is locked away until the current minimum pension age (57, rising to 58 by 2028, and likely to keep rising over time in line with state pension age trends), and withdrawals in retirement are taxed as income, not as capital gains or dividends, with the first 25% of the pot generally available tax-free (subject to a lifetime limit) and the rest taxed at your income tax rate at the time of withdrawal. For retirement-specific savings, the upfront tax relief on contributions is usually the single most powerful tax advantage available anywhere in the UK system, provided the inaccessibility until later in life is actually compatible with the goal the money is being saved for.

In practice, most financial advice suggests prioritising a pension at least up to any employer matching contribution (which is close to a guaranteed 50–100% immediate return on that portion), then deciding between further pension contributions and ISA contributions based on how much you value access to the money before retirement age versus the extra tax relief the pension provides.

Bed and ISA — Moving Existing Holdings Into the Wrapper

Bed and ISA is the process of selling an investment held in a general investment account, and immediately repurchasing the same investment inside an ISA, using that year's ISA allowance. The name comes from an older, similar practice ("bed and breakfasting") that HMRC has since closed off in its original form specifically to prevent abuse — more on that below.

The mechanics matter: selling the investment in the general account is a genuine disposal for CGT purposes, and if it produces a gain above your annual exempt amount, that gain is taxable in the normal way, exactly as if you had sold and kept the cash rather than reinvesting it. The benefit is entirely forward-looking: once the investment sits inside the ISA, all future gains and dividends on it become permanently tax-free, even though the CGT bill (if any) on the historic gain up to the point of the transfer still has to be settled.

Many investors use bed and ISA deliberately, year after year, as a way to gradually migrate a large general investment account into the tax-free wrapper over several tax years, using the annual exempt amount and ISA allowance in combination each year to move across as much as possible without triggering an unnecessary tax bill on any single year's transfer.

Using Losses to Offset Gains

Loss harvesting means deliberately realising a loss on an investment — selling it while it is worth less than you paid — specifically to offset gains made elsewhere in the same tax year, reducing your overall CGT bill. If your losses in a tax year exceed your gains, or if you have no gains to offset them against at all, the unused losses can be carried forward indefinitely to offset gains in future tax years, as long as they are reported to HMRC.

A worked example: you have a £7,000 gain on one holding and a £4,000 loss on another, both realised in the same tax year. Your net gain is £3,000 — which, at time of writing, sits exactly within the annual exempt amount, meaning no CGT is owed at all on either transaction, purely because the loss was realised in the same tax year as the gain. Without harvesting that loss, the £7,000 gain alone would have used up the £3,000 allowance and left £4,000 taxable at 18% or 24%.

It is worth noting that losses must genuinely be reported to HMRC to be usable in future years — a loss that is never declared on a tax return cannot later be claimed retroactively to offset a future gain, which makes keeping accurate records of every disposal, gain, and loss a practical necessity for anyone actively managing investments in a general account.

US Shares and Funds — What Actually Applies to UK Residents

A common misconception is that UK residents owe US tax on US shares. In practice, as a UK tax resident, you pay UK CGT and UK dividend tax on US investments under exactly the same rules covered throughout this chapter — not US capital gains tax, and not US income tax, thanks to the US–UK double taxation treaty.

What you do need to deal with is dividend withholding tax, which the US applies at source before the dividend even reaches you. Without any paperwork, this withholding defaults to 30%. By completing a W-8BEN form with your broker — a standard, one-time form confirming you are not a US taxpayer and claiming the treaty rate — the withholding rate drops to 15%, which you generally cannot reclaim further but which is already factored correctly into the net dividend you receive. Most UK brokers prompt new account holders to complete this automatically, but it is worth checking it has actually been done, since failing to do so leaves an extra 15% of every US dividend withheld permanently and unnecessarily.

Note that the treaty relief applies to shares and most ETFs but can get genuinely complicated around US-domiciled mutual funds and some other structures, and estate tax (a separate US tax triggered on death for holdings of US assets above a threshold) is a distinct consideration for larger US share portfolios that is worth professional advice if it could plausibly apply to you.

Funds: Accumulation vs. Income, and a UK-Specific Wrinkle

UK investment funds commonly come in two versions of the same underlying portfolio: income units, which pay dividends out to you as cash, and accumulation units, which automatically reinvest dividends inside the fund rather than paying them out. Inside an ISA or pension, the choice makes no tax difference at all. In a general investment account, it matters more than most investors realise: even though accumulation units don't pay you cash, the reinvested income is still treated as taxable dividend income in the year it is reinvested, exactly as if it had been paid out and immediately used to buy more units — HMRC does not allow deferring the tax simply because the cash never physically left the fund.

A further wrinkle applies specifically to funds domiciled outside the UK (many global index funds, for instance, are domiciled in Ireland or Luxembourg): if the fund does not have UK "reporting fund" status, any income the fund accumulates internally but doesn't formally report can be taxed as a capital gain rather than dividend income when you eventually sell, and in some non-reporting cases excess gains can even be taxed as income rather than a capital gain at all — a materially worse outcome. Checking that a fund has UK reporting fund status (most major UK-platform-available global funds do) before buying it in a general investment account avoids this complication entirely.

What Happens to Investments on Death

It is worth briefly covering what happens to a portfolio's tax position on death, since it differs meaningfully from lifetime rules and surprises many people who assume CGT simply carries over unchanged. On death, assets (including those in a general investment account) are generally revalued to their market value at the date of death for CGT purposes — meaning any capital gain built up during your lifetime is wiped out for CGT purposes, not inherited by whoever receives the assets. The estate itself may be subject to Inheritance Tax (IHT) on the total value above the available nil-rate bands, but the beneficiary who inherits the investments starts with a fresh CGT cost base equal to the value at the date of death, not the original purchase price.

ISAs have a specific, additional feature on death for a surviving spouse or civil partner: an Additional Permitted Subscription (APS) allowance lets the surviving spouse shelter an amount equal to the value of the deceased's ISA within their own ISA, on top of their normal annual allowance, preserving the tax-free status of that money going forward rather than it losing its wrapper on transfer. This is a genuinely valuable, often under-used provision worth knowing about specifically because it does not happen automatically — the surviving spouse or their adviser needs to actively claim it with the relevant ISA provider.

When You Actually Need to Tell HMRC

Not every disposal needs to be reported. You generally need to report capital gains to HMRC, via a Self Assessment tax return, if any of the following apply in a tax year: your total gains exceed the annual exempt amount (£3,000 at time of writing); your total proceeds from all disposals (not just the gain, the full sale value) exceed four times the annual exempt amount; you have losses to report for use against future gains; or you are otherwise required to file a Self Assessment return for other reasons (such as being self-employed).

1. Keep records of every purchase and sale — date, price, quantity, and any associated costs — for at least the relevant tax year plus several years afterward, since HMRC can request evidence to support a return going back some years.
2. Calculate gains and losses across the whole tax year before working out what, if anything, is owed — remember the single combined allowance covers all general account disposals together, not per holding.
3. Report via Self Assessment by the standard filing deadlines (31 January following the end of the tax year for online returns), even in years where no tax is ultimately due but the reporting thresholds above are met.

Holdings entirely within an ISA or pension never need to be reported at all, regardless of size or gains, which is yet another practical reason the ISA-first approach covered earlier in this chapter reduces ongoing administrative burden as well as the tax bill itself.

Tax-Efficient Strategies, Summarised

When HMRC Treats You as a Trader, Not an Investor

Everything in this chapter assumes you are investing — buying and holding assets with a view to long-term gain, taxed under the Capital Gains Tax regime. HMRC draws a separate, important distinction for people whose activity looks more like running a trading business: very high frequency of transactions, short holding periods, use of borrowed money specifically to fund the activity, and treating it as a primary source of income rather than occasional investment activity. If HMRC decides your activity amounts to "trading" rather than "investing" — assessed against a long-standing set of criteria sometimes informally called the "badges of trade" — profits are taxed as income rather than as capital gains, at your full marginal income tax rate (up to 45% at time of writing) rather than the 18%/24% CGT rates, with no annual exempt amount equivalent to shelter part of it.

This distinction rarely affects an ordinary long-term investor buying and holding shares or funds over years, and HMRC has never published a precise, mechanical test — it is a judgement based on the overall pattern of activity. It is far more relevant to someone engaging in frequent short-term trading, including some of the leveraged and derivative strategies covered elsewhere in this part of the course, since activity that looks more like day trading than long-term investing is exactly the pattern more likely to attract this classification. Anyone trading frequently and at meaningful scale, rather than simply holding a long-term diversified portfolio, should be aware this distinction exists and consider professional advice specific to their own pattern of activity.

Why Every Number in This Chapter Could Be Out of Date

UK investment tax rules have changed substantially and repeatedly in just the past few years: the CGT annual exempt amount fell from £12,300 to £6,000 to £3,000 across three consecutive tax years; the dividend allowance fell from £2,000 to £1,000 to £500 over a similar period; and CGT rates on investment gains were themselves changed at the October 2024 Budget. There is no reason to assume this pattern of change has finished.

Every specific figure in this chapter — the £3,000 CGT allowance, the 18%/24% rates, the £500 dividend allowance, the £20,000 ISA allowance, the pension access age — reflects the rules at time of writing and should be treated as a snapshot, not a permanent fact. Before making any decision where the exact numbers materially change the outcome — a large one-off disposal, a bed and ISA transfer close to a threshold, a decision between pension and ISA contributions — checking HMRC's current published rates directly, or speaking to a qualified adviser, is worth the extra few minutes it takes.