Cash ISA vs stocks and shares ISA: what's the difference?
A cash ISA holds savings that earn interest, so your money stays the same in pounds and grows steadily, though rising prices can erode its spending power over years. A stocks and shares ISA holds investments that can grow more over long periods but can also fall in value. Both shelter returns from UK tax and share one £20,000 yearly allowance.
How does each ISA actually work?
A cash ISA is a savings account with a tax-free wrapper. You put in pounds, the provider pays interest, and the balance in pounds does not fall. It behaves like an ordinary savings account, except the interest is free from UK income tax.
A stocks and shares ISA is an investment account inside the same kind of wrapper. Your money is used to hold things like company shares or funds, such as a broad tracker. The value rises and falls with those markets, and any growth or income is free from UK tax.
Which risks come with each one?
Cash carries what people call inflation risk. If a cash ISA pays 4% while prices rise 3%, your real gain is small; if prices rise faster than the interest, those pounds gradually stretch to less over time. The number on the statement never drops, but its purchasing power can.
A stocks and shares ISA carries market risk. Values can fall, sometimes sharply, and you could get back less than you put in. Over long stretches, invested money has historically tended to grow more than cash, but that history is not a promise, and the ride is bumpy.
How does the £20,000 allowance work across both?
For the 2026/27 tax year the ISA allowance is £20,000, and it is shared across every ISA you hold. You could put the whole £20,000 in one, or split it, say £8,000 in a cash ISA and £12,000 in a stocks and shares ISA.
The allowance resets each 6 April and does not roll over, so anything unused that year is simply gone. Since April 2024 you can also pay into more than one ISA of the same type in a single year, as long as the combined total stays within £20,000.
How does your timeframe change the picture?
Timeframe is usually the deciding factor rather than a hard rule. For money you might need soon, a deposit for a car or a holiday next year, many people value the steadiness of cash, because a market dip at the wrong moment cannot shrink it.
For money you can leave alone for five, ten or more years, investments have more room to recover from falls and let growth compound. Many people use both: cash for near-term safety and a stocks and shares ISA for long-term goals like retirement.
A worked example
Imagine two people each put £10,000 into an ISA. In a cash ISA paying 4% a year, after one year the balance is £10,400, and it never dips below £10,000. In a stocks and shares ISA, a 6% year would lift it to £10,600, but a poor year of minus 10% would drop it to £9,000. Neither pays UK tax on the interest or growth. Over 20 years the steady cash path might reach roughly £21,900, while investments have historically tended to grow faster, though with real falls along the way and no guarantee.
Common questions
Can I have both a cash ISA and a stocks and shares ISA?
Yes. You have always been able to split money across different ISA types in one tax year, and since April 2024 you can also pay into more than one ISA of the same type. The only limit is the shared £20,000 allowance, so your total across every ISA cannot exceed that in 2026/27.
Is my money safe in a stocks and shares ISA?
Your money is invested, so its value moves up and down with markets and can be worth less than you put in. It is not the same as cash savings. The tax shelter protects returns from UK tax, but it does not protect the underlying value from market falls.
Does the type of ISA I choose depend on time?
Time is often the deciding factor rather than a fixed rule. Money needed within a year or two tends to sit more comfortably in cash, where the pounds stay steady. Money left untouched for many years gives investments room to ride out falls, though outcomes are never certain.
Where to next
General information to help you understand investing, not advice about your situation. Figures are illustrative and the rules can change - always check gov.uk or your provider for the latest.