Guide · Savings & Investing
Stocks & Shares ISA vs Cash ISA: Which Builds More Wealth?
The ISA wrapper is one of the best things in UK personal finance — all growth, income, and gains inside it are tax-free forever. The question is which type of ISA to fill, with what, and in what order.
The ISA allowance
Every UK adult gets a £20,000 annual ISA allowance. Money placed inside an ISA grows completely free of income tax and Capital Gains Tax — not just while it is there, but permanently, including on withdrawal. Unused allowance is lost at the end of each tax year (5 April). There is no lifetime cap on ISA balances.
Cash ISA vs Stocks & Shares ISA
| Feature | Cash ISA | Stocks & Shares ISA |
|---|---|---|
| What it holds | Cash deposits | Funds, shares, ETFs, bonds |
| Return type | Interest (AER) | Capital growth + dividends |
| Typical return (long run) | ~4–5% AER (2026) | 7–9% nominal annually |
| Risk of loss | None (FSCS protected) | Yes — value can fall |
| Best for | Goals under 3–5 years | Goals 5+ years away |
| Instant access | Yes (easy-access type) | Yes, but value may be down |
What £10,000 becomes over 20 years
The long-run return difference between cash and equities is dramatic when compounded over two decades:
| Account | Rate assumed | Value after 20 years |
|---|---|---|
| Cash ISA (best easy-access) | 4.5% AER | £24,117 |
| Stocks & Shares ISA (global equity) | 7% nominal | £38,697 |
| Stocks & Shares ISA (global equity) | 9% nominal | £56,044 |
| General Investment Account at 7% | 7% (taxed) | ~£30,200 |
Assumes rates remain constant (they will not). GIA figure estimates CGT impact for a higher-rate taxpayer drawing gains at 24%. All values approximate.
At 7% nominal, a Stocks & Shares ISA produces 60% more wealth than a 4.5% Cash ISA over 20 years. This gap widens significantly with longer horizons. The tax shelter of the ISA wrapper adds further advantage versus a GIA, where annual gains crystallise CGT.
ISA vs pension: which first?
For most people with earned income, the decision order is:
- Contribute enough to your workplace pension to get the full employer match — this is an instant 100% return.
- Build an emergency fund in an easy-access account (not an ISA).
- Pay off high-interest debt.
- Max your pension contributions (SIPP or workplace) for the upfront tax relief.
- Max your ISA allowance (accessible without age restriction).
ISAs win over pensions on flexibility — there is no age restriction on access. Pensions win on tax efficiency — the government adds 20–45% to every contribution. Both should be used; the order depends on your access needs.
Frequently asked questions
What is the ISA allowance for 2026/27?
The annual ISA allowance is £20,000 per adult. You can split this across multiple ISA types in the same tax year — for example, £10,000 in a Cash ISA and £10,000 in a Stocks & Shares ISA — as long as the combined total does not exceed £20,000. The allowance resets each 6 April and cannot be carried forward.
What is the difference between a Cash ISA and a Stocks & Shares ISA?
A Cash ISA holds cash and pays interest, sheltered from income tax. A Stocks & Shares ISA holds investments (funds, shares, ETFs) and shelters both dividend income and capital gains from tax. For goals under 3–5 years, a Cash ISA is usually more appropriate. For goals 5+ years away, a Stocks & Shares ISA typically produces much higher returns due to equity growth.
Can I withdraw from an ISA?
Yes — and withdrawals are tax-free. However, unless you have a 'flexible' ISA, withdrawing money does not restore your allowance for the year. If you put in £20,000 and withdraw £5,000, you have used your full £20,000 allowance even though your balance is now £15,000. A flexible ISA lets you replace withdrawn funds within the same tax year.
What is a Lifetime ISA (LISA)?
A Lifetime ISA allows you to save up to £4,000 per year and receive a 25% government bonus (up to £1,000/year). It can only be used to buy a first home (purchase price up to £450,000) or accessed from age 60. Withdrawing for any other reason incurs a 25% penalty that effectively takes back the bonus and a portion of your own contributions. The £4,000 LISA allowance counts within the overall £20,000 ISA allowance.