TL;DR: A cash ISA holds cash savings that pay interest free of UK income tax. A stocks and shares ISA holds investments (funds, shares, ETFs, investment trusts, bonds) whose growth, dividends and gains are free of UK income tax and capital gains tax. The annual ISA allowance is 20,000 pounds across all adult ISA types combined for the 2026-27 tax year. Cash ISAs suit money needed in the next few years and money intended as protected emergency savings. Stocks and shares ISAs suit money that can stay invested for at least five years and ideally longer, where the higher long-term expected return more than offsets the year-to-year volatility. The right split is not a verdict on which is better; it is a question of when the money will be spent.
Last reviewed May 2026
The Individual Savings Account (ISA) is the UK's main tax-protected wrapper for personal savings and investing. Two types dominate adult ISA balances: cash ISAs, which work like a savings account whose interest does not count as taxable income, and stocks and shares ISAs, which hold investments whose growth and income are sheltered from UK income tax and capital gains tax. The choice between them is a classic personal finance question, and the right answer is almost always "both, in a ratio that matches when the money will be spent".
This guide sets out how each ISA actually works, what the tax position is in 2026, the practical trade-offs between cash and investments, what the historical numbers say about long-term returns, and how to think about splitting the annual 20,000 pound allowance between them.
What a cash ISA is, in practice
A cash ISA is a savings account that sits inside the ISA wrapper. The cash is held with a UK bank or building society, the account pays interest, and the interest does not count towards the saver's personal allowance, personal savings allowance or any other tax limit. The deposit benefits from Financial Services Compensation Scheme (FSCS) protection up to 85,000 pounds per person per banking licence.
Cash ISAs come in four common forms: easy-access (instant withdrawal, variable rate), fixed-rate (a guaranteed rate for a set term, usually with a withdrawal charge if money is taken out early), notice (a specified notice period before withdrawal), and Lifetime ISA in cash (a Lifetime ISA can be held as cash or as stocks and shares; the LISA itself is a separate product with a 4,000 pounds annual sub-limit and a 25 percent government bonus). Junior cash ISAs are a separate product for under-18s.
The headline rates change with the Bank of England base rate. After several years of rates above 4 percent on best-buy easy-access and fixed cash ISAs, the picture in 2026 depends on where base rate sits. Comparison tables on MoneyHelper and the FCA-regulated comparison sites show the current best-buy rates.
What a stocks and shares ISA is, in practice
A stocks and shares ISA is a brokerage account that sits inside the ISA wrapper. The investor uses the account to hold investments: open-ended funds (OEICs), unit trusts, exchange-traded funds (ETFs), investment trusts, individual shares, corporate and government bonds, and (subject to platform rules) some other allowable holdings. Any growth, dividend or interest the investments produce is free of UK income tax and capital gains tax. There is no need to report holdings to HMRC.
The account is held on a platform (an ISA provider). The platform charges a fee for holding the account, the funds inside it have their own annual charges (usually expressed as the ongoing charges figure, or OCF), and there can be dealing charges on share trades. The total cost is sometimes called the reduction in yield.
The investments inside the ISA can go down as well as up. There is no FSCS payout if a stock falls or a fund's value drops; FSCS protection covers the failure of the platform or fund provider, not investment performance. Investments held on a UK platform that fails would normally either be transferred to another firm or refunded up to the 85,000 pound investment limit, depending on the circumstances.
The tax position in 2026
For the 2026-27 tax year, the adult ISA allowance is 20,000 pounds across all types combined. That means the 20,000 pounds can be split in any ratio between a cash ISA, a stocks and shares ISA, an innovative finance ISA and a Lifetime ISA (capped at 4,000 pounds), provided the total does not exceed 20,000 pounds. From the 2024-25 reforms, savers can pay into multiple ISAs of the same type within the same tax year (subject to provider rules), which makes splitting and switching easier than in earlier rules.
Interest inside a cash ISA is paid free of income tax regardless of total interest received or income tax band. Outside an ISA, the personal savings allowance (1,000 pounds for basic-rate taxpayers, 500 pounds for higher-rate taxpayers, zero for additional-rate taxpayers) and the starting rate for savings can shelter some interest from tax, but anything above those allowances is taxed at the saver's marginal rate.
Growth and dividends inside a stocks and shares ISA are free of UK income tax and capital gains tax. Outside an ISA, the dividend allowance has fallen to 500 pounds for 2024-25 onwards and the annual CGT exemption has fallen to 3,000 pounds, so the ISA tax shelter is much more valuable than it was a decade ago. Foreign dividends paid into an ISA are still subject to withholding tax in the country of source (commonly 15 percent on US dividends under the W-8BEN treaty rate); the ISA shelter is from UK tax, not foreign tax.
Risk, return and time horizon
The cash ISA's main risk is purchasing-power risk: if inflation runs above the savings rate, the buying power of the balance falls in real terms even though the cash number is unchanged. The 2022-23 inflation spike meant cash returns lagged price rises by a wide margin. Cash does not carry capital risk in the way investments do; the balance does not fall in nominal terms, and FSCS protection covers up to 85,000 pounds.
The stocks and shares ISA's main risk is volatility: the value of the investments inside it can fall sharply over short periods. UK and global equity drawdowns of 30 to 50 percent inside a single year have happened multiple times in the last 50 years. A diversified global portfolio has historically recovered from these drawdowns within several years and produced a long-term real return above cash, but the path is not smooth.
Time horizon is what reconciles the two. Money needed inside three years is normally held in cash, because the cost of a 30 percent drop within that window is too high relative to the modest expected outperformance. Money that can stay invested for 10 years or more has historically done better in a diversified equity portfolio than in cash, although past performance is not a reliable guide to future returns and an investment can finish lower than it started over any specific period.
Splitting the 20,000 pound allowance
The pragmatic split for most savers follows their spending plans, not a rule of thumb. Money allocated to emergency reserves, to a planned house deposit, to a fixed near-term spend, or simply needed flexible goes into the cash ISA. Money allocated to long-term goals (retirement supplement, decades-distant spending) goes into the stocks and shares ISA.
Tax considerations sharpen the split in two cases. A higher-rate or additional-rate taxpayer with cash savings already producing more than 500 pounds of interest a year (or none of personal savings allowance left) gets immediate tax relief by moving the next pound of cash into a cash ISA. An investor producing more than 500 pounds of dividends a year, or with gains likely to exceed the 3,000 pound CGT exemption, gets the most benefit by holding investments inside a stocks and shares ISA first and a general investment account second.
Lifetime ISAs add another dimension for under-40s saving for a first home or retirement. The 4,000 pound Lifetime ISA sub-limit attracts a 25 percent government bonus (up to 1,000 pounds a year) and can be held as cash or as investments. The penalty for withdrawing for any purpose other than a qualifying first-home purchase or after age 60 is 25 percent of the amount withdrawn, which is more than the bonus.
Transfers and the rules that catch people out
Money already in an ISA from previous tax years can be transferred between cash and stocks and shares ISAs without using new allowance. The transfer must be done provider-to-provider; withdrawing the money and re-depositing it would use that year's allowance. Most providers complete a cash ISA to cash ISA transfer in 15 working days and a cash to stocks and shares (or vice versa) transfer in 30 calendar days, under HMRC and FCA expectations.
Fixed-rate cash ISAs usually have a withdrawal charge for early access (typically loss of interest), and that charge can apply even when transferring out before maturity. Some providers waive the charge on transfer at maturity if the transfer instruction is in place in time. The terms and conditions for the specific account state the position.
From 2024-25 onwards, multiple subscriptions to ISAs of the same type within the same tax year are allowed. The total across all ISAs still cannot exceed 20,000 pounds, and the Lifetime ISA 4,000 pound sub-limit still applies. Provider-specific rules can still apply (some providers do not accept new money into an account that has already received subscriptions in the same year), so the ISA provider should be checked before splitting.
How we verified this
The rules in this article reflect the ISA framework set out in the Individual Savings Account Regulations 1998 (as amended), the HMRC ISA guidance for managers and savers, the 2024-25 reforms to ISA flexibility, the 2024 reduction in the dividend allowance to 500 pounds and the CGT exemption to 3,000 pounds, and the FCA expectations on transfer timescales. The FSCS deposit and investment protection limits reflect the current statutory limits. Headline cash savings rates change in response to Bank of England base rate moves and should be checked against current best-buy comparisons on MoneyHelper or another FCA-regulated comparison source rather than against any figure quoted here.
Disclaimer: This article is general information about cash ISAs and stocks and shares ISAs in the UK. It is not personal financial advice. The right split between cash and investments depends on personal circumstances, time horizon, tax position and risk tolerance. Anyone making material decisions should check the current HMRC ISA rules, the specific provider terms, and either take advice from an FCA-authorised adviser or use the free guidance from MoneyHelper.
Frequently asked questions
Can I have a cash ISA and a stocks and shares ISA in the same tax year?
Yes. The 20,000 pound annual allowance is the combined limit across all ISA types, but it can be split between a cash ISA, a stocks and shares ISA, an innovative finance ISA and a Lifetime ISA (which has its own 4,000 pound sub-limit). From 2024-25 onwards, multiple subscriptions to ISAs of the same type in a single year are allowed under HMRC rules, subject to specific provider terms.
Which is better, a cash ISA or a stocks and shares ISA?
It depends on when the money is needed. Cash ISAs protect short-term value and pay tax-free interest. Stocks and shares ISAs have produced a higher real return over long periods but can fall in any given year. Money needed inside three years is normally held in cash; money that can stay invested for 10 years or more has historically benefited more from a diversified investment portfolio than from cash, although past performance is not a reliable guide.
Do I pay tax on a cash ISA or a stocks and shares ISA?
No UK income tax on cash ISA interest. No UK income tax or capital gains tax on stocks and shares ISA growth, dividends or gains. Foreign dividends paid into a stocks and shares ISA can still have withholding tax applied at source (15 percent on US dividends under treaty rates). Holdings inside an ISA do not need to be reported on a UK self-assessment tax return.
Can I transfer between a cash ISA and a stocks and shares ISA?
Yes. Previous-year ISA money can be transferred between cash and stocks and shares ISAs without using new allowance, as long as it is done provider-to-provider rather than by withdrawing and re-depositing. Most cash-to-cash transfers complete within 15 working days and cross-type transfers within 30 calendar days under HMRC and FCA expectations. Fixed-rate cash ISAs can have an interest charge for early transfer.
What happens to my ISA if I die?
The ISA tax wrapper continues for up to three years after death (or until the estate is closed, if earlier) as a continuing ISA, so growth and interest stay tax-free during that period. A surviving spouse or civil partner can inherit an additional permitted subscription equal to the value of the deceased spouse's ISA on the date of death, which can be used on top of the normal 20,000 pound allowance.
