Money held inside an Individual Savings Account is free from UK income tax on interest, tax on dividends, and capital gains tax on any growth. That is the whole shelter, and it applies for as long as the money stays inside the ISA wrapper. The one tax on ISA savings that does still bite is inheritance tax: when you die, your ISA balance is counted in your estate like any other asset. Everything below explains how each of those pieces works.
What’s Tax-Free Inside an ISA
Three taxes fall away as soon as money sits inside an ISA.
Interest on cash held in an ISA is exempt from income tax. A Cash ISA paying 5% pays you the full 5%, with no deduction at any tax band. Dividends paid by shares or funds held in a Stocks and Shares ISA arrive tax-free, instead of being charged at the dividend rates of 8.75% to 39.35% that apply outside the wrapper. And any growth in the value of ISA investments is shielded from capital gains tax: a holding that grows from £10,000 to £100,000 can be sold in full with nothing owed to HMRC.1GOV.UK. Individual Savings Accounts – How ISAs Work
The exemptions come from Regulation 22 of the Individual Savings Account Regulations 1998, which provides that no tax is chargeable on interest, dividends, distributions, or gains in respect of ISA investments.2Legislation.gov.uk. The Individual Savings Account Regulations 1998
You also don’t have to tell HMRC about any of it. ISA interest, ISA income, and ISA capital gains never appear on your tax return.1GOV.UK. Individual Savings Accounts – How ISAs Work
How This Compares to the Personal Savings Allowance and Dividend Allowance
Outside an ISA, some savings income is already tax-free thanks to two separate allowances. The Personal Savings Allowance lets basic-rate taxpayers earn up to £1,000 in savings interest tax-free, higher-rate taxpayers up to £500, and additional-rate taxpayers nothing at all. Interest earned inside an ISA does not count towards the PSA, so the two allowances run in parallel.3GOV.UK. Tax on Savings Interest – How Much Tax You Pay
Dividends outside an ISA are covered by a much smaller allowance: £500 a year before tax kicks in at the rates noted above.4GOV.UK. Check if You Have to Pay Tax on Dividends Inside an ISA there is no dividend cap.
For a modest saver whose interest falls well below the PSA, the immediate tax benefit of a Cash ISA is small. The value grows over time: ISA money stays tax-free no matter how large the balance becomes, whatever future tax bands do, and whatever happens to the PSA itself. Higher-rate taxpayers, and anyone whose savings are growing past the PSA, feel the shelter sooner.
Capital gains work the same way. Outside an ISA, gains above the annual exempt amount (£3,000 for individuals in the 2025–26 and 2026–27 tax years) are taxable.5HM Revenue & Customs. Capital Gains Tax Rates and Allowances Inside, the limit is irrelevant.
How Much You Can Shelter Each Year
The maximum you can deposit across all your ISAs in a single tax year is £20,000. The tax year runs from 6 April to 5 April, and any unused allowance disappears once the new year begins. It doesn’t roll over.1GOV.UK. Individual Savings Accounts – How ISAs Work
The £20,000 is shared across Cash, Stocks and Shares, Innovative Finance, and Lifetime ISAs. Since April 2024, you can open more than one ISA of the same type in the same tax year, provided your combined contributions stay within the £20,000 ceiling.
Some ISAs are classified as “flexible,” which means you can withdraw cash and put it back within the same tax year without using up any more of your allowance. Not every provider offers this, so check before you rely on it.6GOV.UK. Individual Savings Accounts – Withdrawing Your Money
If You Pay In Too Much
Going over £20,000 triggers a repair. If the excess is caught in the current tax year, your provider can advise you to remove the extra contribution along with any income or gains it produced; you get to choose which subscriptions to pull. For breaches spotted in a later year, HMRC contacts you and the provider directly, and the provider won’t act without that formal notice. The valid portion of the ISA keeps its tax-exempt status, but income earned on the excess loses its tax protection. If the account can’t be repaired, HMRC voids it entirely and the whole invalid subscription plus its income has to come out.7GOV.UK. How to Close, Void or Repair an ISA
Losses Inside an ISA Don’t Count Either
The tax shield cuts both ways. Because gains inside an ISA aren’t taxable, losses inside an ISA are disregarded for capital gains tax. You cannot use an ISA loss to offset a taxable gain made on assets held outside the wrapper. Investors sometimes overlook this when weighing whether to hold a volatile position inside or outside their ISA.
Inheritance Tax: The One Tax an ISA Doesn’t Escape
When you die, the full value of your ISA is included in your estate for inheritance tax. If the estate exceeds the nil-rate band of £325,000, frozen at that level until at least April 2030, the excess is charged at 40%.8GOV.UK. Inheritance Tax Thresholds and Interest Rates ISA balances get no special exemption; they’re treated the same as any other asset in the estate.
A residence nil-rate band of £175,000 can apply when a qualifying home passes to direct descendants, potentially lifting the effective threshold to £500,000 per person. Married couples and civil partners can transfer unused nil-rate bands between them, which can shield up to £1 million in combined circumstances.9GOV.UK. Inheritance Tax Thresholds
The Additional Permitted Subscription for a Surviving Spouse
One relief targets ISA holders’ families specifically. When an ISA holder dies leaving a spouse or civil partner, the survivor gets an Additional Permitted Subscription allowance equal to the higher of the ISA’s value at the date of death or its value when the ISA ceases to be a “continuing account.” The APS is separate from the survivor’s own £20,000 annual limit, so the inherited amount can be sheltered without using up their normal allowance. It must be used within three years of the date of death, or within 180 days of the estate administration completing, whichever is later.
AIM Shares and Business Property Relief
Some investors hold shares listed on the Alternative Investment Market inside their ISAs to reduce inheritance tax. Qualifying AIM shares have historically attracted Business Property Relief at 100% after a two-year holding period, taking them out of the estate for inheritance tax. From 6 April 2026, the rate of BPR on AIM and other unlisted exchange-traded shares drops to 50%, producing an effective inheritance tax rate of 20% rather than zero.10GOV.UK. Agricultural Property Relief and Business Property Relief Changes The two-year holding period still applies, the shares have to be held at death, and not every AIM company qualifies. Eligibility can also change if a company’s activities shift.
Don’t Lose the Tax Wrapper by Accident
An ISA’s tax protection lasts only while the money stays inside an ISA. There is one common mistake that ends it: withdrawing ISA money into a regular bank account with the intention of putting it into a different ISA later. The moment cash leaves through a manual withdrawal, it loses its protected status. Putting it back counts as a fresh contribution against your current year’s £20,000 allowance.11GOV.UK. Individual Savings Accounts – Transferring Your ISA
The safe route is a provider-to-provider transfer. Contact the new provider, complete their ISA transfer form, and let them handle the move with your old provider. You can transfer the full balance or a partial amount. Regulated maximum timelines are 15 working days for Cash ISA to Cash ISA transfers and 30 calendar days for other transfers.11GOV.UK. Individual Savings Accounts – Transferring Your ISA
For a Stocks and Shares ISA, a cash transfer sells the holdings, moves the money across, and you reinvest at the other end. Because sales inside the wrapper don’t trigger capital gains tax, this doesn’t create a tax bill, which is why it’s the more common option. An in-specie transfer moves the actual investments across without selling them, which avoids time out of the market but takes longer and only works when the new provider carries the same funds or share classes.