UK Stocks and Shares ISA Calculator

What Is a Stocks and Shares ISA?

A Stocks and Shares ISA is a UK tax wrapper that lets you invest in shares, ETFs, funds, bonds and investment trusts without paying income tax on dividends, capital gains tax on profits or any tax on interest. The wrapper is what makes it powerful, not the investments inside it, which can be anything from individual FTSE 100 shares to global index funds.

For most UK long-term investors, a Stocks and Shares ISA is the single most valuable account available outside a workplace pension. Putting in £20,000 a year into a global equity ETF averaging 7% net for 30 years produces a pot where every penny of the growth is fully tax-free, no capital gains tax on sale, no dividend tax on income drawn in retirement.

ISA Allowance 2025/26 and 2026/27

The ISA allowance for 2026/27 is £20,000. You can split the ISA allowance across any combination of different ISAs but it is your responsibility to ensure you stay within the £20,000 limit.

Key rules for the 2026/27 tax year:

Rule

Detail

Annual allowance

£20,000 total across all ISA types

Junior ISA allowance

£9,000 per child per year

Lifetime ISA limit

£4,000 per year (within the £20,000 overall cap)

Cash ISA from April 2027

Maximum £12,000 for under-65s from next year

Use by

Midnight on 5 April, unused allowance is lost

Number of ISAs

You can now pay into multiple ISAs of the same type per year

Transfers

ISA transfers do not count against your annual allowance

April 2027 rule change: From April 2027, investors under 65 will be limited to a maximum of £12,000 in a Cash ISA within the overall £20,000 allowance, with any additional amount required to go into an investment ISA. This change is designed to encourage more long-term investment rather than cash saving. The 2026/27 tax year has no such restriction, you can still put the full £20,000 into a Cash ISA if you choose.

Why the ISA Wrapper Matters So Much in 2026

Two tax changes have made the ISA wrapper more valuable than ever for UK investors.

Capital Gains Tax allowance collapsed: The annual CGT-free allowance has fallen from £12,300 in 2022/23 to just £3,000 in 2024/25 and remains at £3,000 for 2026/27. Gains inside an ISA are entirely CGT-free and do not count toward this allowance. Outside an ISA, even a modest investment portfolio that has grown can trigger a tax liability when shares are sold.

Dividend allowance cut to £500: The tax-free dividend allowance has been reduced from £5,000 in 2017/18 to just £500 for 2026/27. Above £500, dividends are taxed at 8.75% for basic rate taxpayers and 33.75% for higher rate taxpayers. Dividends received inside an ISA are completely tax-free with no cap.

The practical implication is straightforward: there is almost never a reason to hold dividend-paying shares or investments likely to generate capital gains outside an ISA if you have unused ISA headroom.

The Tax Saving : A Real-World Comparison

Here is what the difference looks like for a higher-rate taxpayer with a £50,000 portfolio generating 4% dividend income and 7% capital gain annually over 10 years.

What You Can Hold Inside a Stocks and Shares ISA

A Stocks and Shares ISA can hold a wide range of investment types:

You can hold: UK and international shares listed on recognised exchanges, exchange-traded funds (ETFs), investment trusts, unit trusts and OEICs, government and corporate bonds and gilts, fractional shares (explicitly supported under updated 2024 rules), REITs.

You cannot hold: Cryptocurrency, CFDs, spread bets, unlisted shares, options, futures. From 6 April 2026, new purchases of cryptoasset exchange-traded notes (cETNs) are no longer permitted inside a Stocks and Shares ISA.

ISA Transfer Rules : Moving Without Losing Tax Protection

Transferring an existing ISA to a new provider does not count against your annual allowance, provided you use the formal transfer process.

Never withdraw funds and redeposit yourself, this consumes new annual allowance for the reinvested amount and permanently loses the tax-free status of the withdrawn funds. Always instruct your new provider to initiate the transfer directly. Cash transfers typically take 2 to 3 weeks. In-specie transfers (moving investments without selling) take 4 to 6 weeks.

Bed and ISA strategy: If you hold shares outside an ISA and want to move them in, you must sell them (potentially triggering CGT on any gain above £3,000), transfer the cash into your ISA, and repurchase the shares inside. This process systematically migrates a non-ISA portfolio into the tax-free wrapper, using up to £3,000 of CGT allowance each year without a tax bill.

Common ISA Mistakes to Avoid

Leaving the allowance unused on 5 April: the allowance expires at midnight on 5 April every year without exception. Even a small annual contribution started early compounds dramatically over time versus waiting.

Holding cash inside a Stocks and Shares ISA indefinitely: having ISA funds sitting in cash earns minimal return and wastes the compounding potential of the tax-free wrapper.

Concentrating heavily in a single stock: ISAs offer no downside protection. Holding a large proportion in one company (particularly your employer's shares) eliminates the diversification benefit that makes long-term investing reliable.

Panicking and withdrawing in a downturn: withdrawing from an ISA during a market correction locks in losses and permanently reduces the tax-free pot unless you have a flexible ISA that allows replacement of withdrawn funds in the same tax year.

Over-paying in fees: actively managed funds within an ISA can charge 1% to 1.5% annually in ongoing charges. A global index tracker ETF covering thousands of companies typically charges 0.07% to 0.20% and has historically outperformed the majority of actively managed funds over a 10-year or longer period.

Lifetime ISA

For investors under 40, the Lifetime ISA (LISA) offers a 25% government bonus on contributions up to £4,000 per year, a maximum bonus of £1,000 annually. This £4,000 sits within the overall £20,000 ISA allowance, not on top of it.

The LISA can be used tax-free for a first property purchase up to £450,000 or for retirement income after age 60. Withdrawing for any other reason triggers a 25% penalty, which in practice slightly exceeds the bonus received. For first-time buyers with a clear property target under £450,000, the LISA bonus represents a strong guaranteed return on top of investment growth inside the wrapper.

Related Calculators

• UK Dividend Yield Calculator
• UK Dividend Tax Calculator
• UK Capital Gains Tax Calculator
• Investment Growth Calculator

References

1. MoneyHelper. Stocks and Shares ISAs. moneyhelper.org.uk, June 2026
2. Hargreaves Lansdown. ISA Allowance 2026/27. hl.co.uk, April 2026
3. AJ Bell. ISA Rules 2026/27. ajbell.co.uk
4. Moneyfarm. Are ISA Dividends Tax Free? blog.moneyfarm.com, January 2026
5. SalaryTax.uk. UK Tax-Free Savings and Investment Allowances 2026/27. salarytax.uk, April 2026
6. SmartInvestorUK. Stocks and Shares ISA Rules 2026. smartinvestoruk.co.uk, March 2026
7. GOV.UK. Individual Savings Accounts (ISAs). gov.uk

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