Stocks ISA vs Cash ISA: What to Know for 2026
Verdict
Stocks ISA wins
Confidence: High
Break point: Equity return must stay above 4.5% every year over 10 years.
The rate that changes everything
The gap between stocks ISA and cash ISA terminal value widens significantly over longer horizons — compounding is the deciding factor.
The break-even equity return of 4.5% is the critical threshold that determines the superiority of the Stocks ISA over the Cash ISA; returns below this rate favor the Cash ISA, while returns above it decisively benefit the Stocks ISA. Given that the Cash ISA offers a guaranteed return of 4.5%, any equity return below this level renders the Stocks ISA less attractive due to its inherent risks. Conversely, if the Stocks ISA achieves returns exceeding 4.5%, it outperforms the Cash ISA, making it the clear winner for investors seeking higher growth potential. Therefore, focus on achieving returns above this benchmark to maximize investment effectiveness.
Worked example
Worked example (illustrative): £5,000/year invested over 10 years. At 7.0% equity return: Stocks ISA = £69,082. At 4.5% cash ISA rate: Cash ISA = £61,441. Stocks ISA produces £7,641 more. Verdict: Stocks ISA wins. Break-even equity return: 4.5%.
When this flips
This flips only when equity returns must stay above 4.5% every year over the full 10-year horizon. If the horizon shortens or the cash ISA rate rises, the attractiveness of equities diminishes relative to safer cash alternatives.
What to do next
| Your situation | Action | Why |
|---|---|---|
| Equity return above break-even | Stocks ISA | Expected return clears the hurdle — compounding wins over the horizon |
| Equity return below break-even | Cash ISA | The certain cash rate beats the uncertain equity return at this level |
| Short horizon under 5 years | Lean cash ISA | Insufficient time to smooth equity volatility — certainty has higher value |
| Long horizon over 15 years | Lean stocks ISA | Compounding over a long runway makes the break-even much easier to clear |
Sources and provenance
Data as of: 2026-04-06
