What is an ISA?
What you'll learn
Understand what an ISA is, why the tax wrapper matters, and the main types.
An ISA is not an investment. It is a tax wrapper: a box you put savings or investments inside, where any interest, dividends or growth is sheltered from UK tax. Over years of compounding, that shelter is worth real money.
The main types
| ISA type | What it holds | Best for |
|---|---|---|
| Cash ISA | Savings | Money you need soon |
| Stocks and shares ISA | Investments | Long-term money |
| Lifetime ISA | Savings or investments | A first home or later life |
| Innovative Finance ISA | Peer-to-peer loans | Higher risk, few beginners |
The allowance
You can pay in up to the ISA allowance each tax year, currently £20,000 across all your ISAs combined (2026/27). The tax year runs 6 April to 5 April, and the allowance does not roll over: if you do not use it, you lose it. Allowances change at Budgets, so check the current figure on gov.uk.
Why it matters
For most people building wealth, the order is simple: fill the tax-free wrapper before investing anywhere taxable. A stocks and shares ISA is where many UK beginners hold their first index fund.
Key takeaways
- An ISA is a tax wrapper, not an investment - what you hold inside still matters.
- Growth, dividends and interest inside an ISA are free of UK tax.
- The main types are cash, stocks and shares, Lifetime and Innovative Finance.
- There is an annual allowance (£20,000 for 2026/27) that does not roll over.
Illustrative only: £10,000 at 6% a year for 20 years. The taxed bar assumes some tax drag along the way; your actual outcome depends on your circumstances and is not a forecast.
Frequently asked questions
Is an ISA an investment?
No. An ISA is a wrapper. What you hold inside it - cash, funds, shares - is what actually grows or earns interest.
Can I have more than one ISA?
Yes. You can hold and pay into different ISAs, but the annual allowance applies across all of them combined.
What is the difference between a cash ISA and a stocks and shares ISA?
A cash ISA works like a tax-free savings account. A stocks and shares ISA holds investments whose growth and dividends are tax-free, and is suited to long-term money.
General information, not financial advice. The value of investments can fall as well as rise, and figures and rules can change; check the current position before acting.