Cash ISA vs stocks and shares ISA

A cash ISA holds savings that earn interest, and the balance never falls. A stocks and shares ISA holds investments such as funds and shares, which can rise and fall in value but have historically grown more over the long term. Both are tax-free and both draw on the same £20,000 annual allowance. The choice comes down to one question: when do you need the money? For the next few years, lean cash. For money you can leave untouched for five years or more, the stocks and shares side has the better odds.

Cash vs stocks and shares ISA, side by side

Both are tax-free wrappers that sit inside the same £20,000 allowance. The difference is what they hold and how the money behaves. Here is the head-to-head on the things that actually decide it.

What a cash ISA is

A cash ISA is a savings account where the interest is tax-free. You put money in, it earns a rate of interest, and the balance only ever goes up. It works much like an ordinary savings account, with the difference that you never pay income tax on the interest, no matter how much you hold or what tax band you are in.

The trade-off is the return. Cash interest tends to be modest, and over long stretches it can struggle to keep pace with rising prices, meaning the buying power of your money slips even as the balance grows. What you get in exchange is certainty: the figure on your statement is the figure you will have, and you can usually get at it quickly. Your deposits are protected by the Financial Services Compensation Scheme up to £120,000 per banking licence, so for money you cannot afford to lose, a cash ISA is the safe home. To see how interest builds a balance over time, the savings calculator shows the path month by month, and how savings grow walks through what drives it.

What a stocks and shares ISA is

A stocks and shares ISA is an account that holds investments rather than cash: typically funds, which pool lots of company shares together, plus individual shares and bonds. Any growth, dividends and interest inside it are tax-free, exactly like a cash ISA. The crucial difference is that the value goes up and down with the markets your investments track.

That movement is the whole bargain. Because your money is invested rather than sitting as cash, it has historically grown more than savings interest over long periods, and reinvested returns compound on top of each other. But there is no guarantee, the value can fall as well as rise, and in a bad year it can drop sharply. The Financial Services Compensation Scheme covers you up to £85,000 if the firm holding the account fails, but it does not cover losses from the market going down, because that is an ordinary part of investing. To get a feel for how compounding growth can build over the years, try the compound interest calculator, and how compound interest works explains why time matters so much.

Risk and return: the real difference

The split between the two ISAs is really a split between certainty and growth. A cash ISA gives you certainty and a lower return. A stocks and shares ISA gives up certainty for the chance of a higher return over time.

With cash, the risk is quiet: your balance is safe, but its buying power can be eroded by rising prices over the years. With stocks and shares, the risk is visible: the value moves around, sometimes a lot, and you have to be willing to see it fall without panic-selling. Over short periods that movement is the bigger danger, because you might need the money at a low point. Over long periods, history suggests the bigger danger is cash quietly losing ground to inflation. Neither is risk-free, they just carry different risks, which is why the time you can leave the money invested matters more than anything else.

Which one suits you, by time horizon

The single most useful test is how long you can leave the money alone. Risk tolerance and your wider finances matter too, but time horizon does most of the deciding.

• Need it within five years. A house deposit, a wedding, an emergency fund, a known bill coming up. Lean firmly towards a cash ISA. You cannot risk the value being down at the moment you need it.
• Five years or more, and you will not touch it. Long-term goals such as a pension top-up or a child\'s future. A stocks and shares ISA has time to ride out the dips and let growth compound, so the odds favour it.
• Somewhere in between, or both at once. Plenty of people keep an emergency buffer and short-term savings in cash, and invest money they will not need for years in stocks and shares. You do not have to pick one.

A practical first move is to make sure you have a cash safety net you could live on for a few months before investing anything you cannot afford to lose.

You do not have to choose: you can hold both

Cash and stocks and shares ISAs are not an either-or. Both sit inside your £20,000 ISA allowance, and you can pay into both in the same tax year as long as the total new money across all your ISAs stays within £20,000. For example, you could put £5,000 in a cash ISA and £15,000 in a stocks and shares ISA, or any other split that adds up to the allowance.

That makes the two a natural pairing rather than rivals: cash for the money you might need soon, investing for the money you can leave to grow. If you already hold a cash ISA and decide some of it should be invested, you can move it across using an ISA transfer. Ask the new provider to transfer it rather than withdrawing the cash yourself, so it stays inside the tax-free wrapper and does not eat into this year\'s allowance.

Tax and fees

On tax, the two are identical, and that is the point of an ISA. Inside either wrapper you pay no income tax on cash interest, no tax on dividends, and no capital gains tax on any growth. You do not even have to declare ISA interest, income or gains on a tax return.

Fees are where they differ. A cash ISA usually has no charges, you simply earn the interest rate on offer. A stocks and shares ISA normally carries costs: a platform charge for the account and ongoing charges on the funds you hold. These are typically small as a percentage, but they come off your returns every year, so they are worth comparing before you commit. None of this changes the tax-free status, it just nibbles at the growth on the investing side. As ever, these figures are general information to help you weigh it up, not financial advice, so confirm the details and any fees with the provider before you decide.

Common questions

Is it better to have a stocks and shares ISA or a cash ISA?

Neither is better in every case, because they do different jobs. A cash ISA pays interest and your balance does not fall, so it suits money you might need within the next few years or cannot afford to lose. A stocks and shares ISA holds investments that can rise and fall in value, and has historically grown more than cash over the long term, so it suits money you can leave invested for at least five years and ideally longer. The honest answer is that it depends on when you need the money and how comfortable you are with the value going down on the way.

Can I put £20,000 in a cash ISA and £20,000 in a stocks and shares ISA in the same year?

No. The £20,000 ISA allowance for the 2026/27 tax year is a single shared limit across all your ISAs, not £20,000 per type. You can split it however you like, for example £15,000 in a cash ISA and £5,000 in a stocks and shares ISA, but the two together cannot add up to more than £20,000 of new money in one tax year. Money already sitting in ISAs from previous years does not count towards this year's allowance.

What is the average return on a stocks and shares ISA over 10 years?

There is no fixed or guaranteed figure, because a stocks and shares ISA can hold very different investments and returns swing from year to year. Over long periods, broad stock-market investing has historically returned more than cash savings, but past performance does not predict the future and some ten-year stretches have been poor. The value can fall as well as rise, and you could get back less than you put in. Treat any single average return number you see as a rough guide, not a promise.

Is a stocks and shares ISA safe?

It is safe from tax and, if the investment firm holding it fails, your eligible money is protected by the Financial Services Compensation Scheme up to £85,000. What it is not protected against is the market falling. If the investments inside it drop in value, that is a normal part of investing and no compensation scheme covers it. That is the key difference from a cash ISA, where the balance does not fall and deposits are protected up to £120,000 per banking licence.

Can I move money from a cash ISA to a stocks and shares ISA?

Yes, through an ISA transfer. You ask the new provider to transfer the money across rather than withdrawing it yourself, which keeps it inside the tax-free ISA wrapper and does not use up this year's £20,000 allowance. Withdrawing the cash and paying it back in would instead count as a fresh contribution against your allowance, so always use the formal transfer process. You can also transfer the other way, from a stocks and shares ISA back to cash.

Do I pay tax on a cash ISA or a stocks and shares ISA?

No. Inside either type of ISA you pay no income tax on cash interest, no tax on dividends, and no capital gains tax on any growth. You also do not have to declare ISA interest, income or gains on a tax return. That tax-free treatment is the whole point of an ISA and it applies the same way to both the cash and the stocks and shares versions.

About this article

Written by the calcd team. We build UK money calculators and explain the numbers behind them in plain English. We checked the £20,000 ISA allowance for the 2026/27 tax year, the rule that you can split it across ISA types, and the tax-free treatment of interest, dividends and gains against gov.uk as the primary source. The Financial Services Compensation Scheme limits (£120,000 per banking licence for cash deposits, and £85,000 for the failure of an investment firm, which does not cover market falls) are from the FSCS. Return comparisons are kept general on purpose: investments can fall as well as rise, past performance does not predict the future, and you could get back less than you put in. Everything here is general information to help you decide, not financial advice, so confirm the details with a provider or a regulated adviser before acting. Last updated June 2026.