Premium Bonds vs Cash ISA 2026/27: Which Actually Gives a Better Return?
Premium Bonds have a headline 'prize rate' that isn't a guaranteed return, while a Cash ISA pays a known rate, tax-free. Here's how the expected returns actually compare, and who each option suits.
How Each Product Actually Works
Premium Bonds (issued by NS&I, government-backed) don't pay interest in the conventional sense. Instead, each £1 bond is entered into a monthly prize draw, with prizes ranging from £25 up to two £1 million jackpots each month. NS&I sets an annualised "prize rate" — currently around 4.4% — which represents the average payout across all bonds in issue, not what any individual bondholder can expect to receive.
A Cash ISA pays a defined interest rate (fixed or variable, depending on the product) directly into the account, with all interest completely tax-free and no lottery element — every saver with the same balance and rate earns the same return.
Why the Prize Rate Isn't What Most People Actually Get
Because prizes are allocated by random draw weighted by the number of bonds held, the "average" 4.4% rate is skewed by a small number of very large prizes (including the two £1 million jackpots each month). Most individual bondholders, especially those with smaller holdings, receive well below the average — many in a typical year receive nothing at all.
| Holding | Approximate chance of winning anything in a year (illustrative) |
|---|---|
| £100 | Low — a small number of £25 prizes possible, many years with no win |
| £1,000 | Moderate — a few small prizes likely across a year on average |
| £10,000 | Higher — multiple small prizes likely, larger prizes still rare |
| £50,000 (max holding) | Consistent stream of smaller prizes typical, large prizes still rare |
NS&I itself publishes the underlying odds per £1 bond per monthly draw — these odds don't scale evenly with the "average" 4.4% headline figure for smaller holders, who typically experience a lower effective return with higher variance.
Head-to-Head Comparison
| Feature | Premium Bonds | Cash ISA |
|---|---|---|
| Return type | Random prize draw, average ~4.4% | Fixed/known interest rate |
| Tax treatment | 100% tax-free, no limit | 100% tax-free, no limit |
| Capital security | 100% Treasury-backed, unlimited | FSCS-protected up to £85,000/institution |
| Access | Can cash in anytime (few working days) | Depends on product — easy access or fixed-term |
| Minimum holding | £25 | Varies by provider, often £1+ |
| Maximum holding | £50,000 per person | £20,000/year new contributions (2026/27 ISA allowance) |
| Predictability | Low — individual outcome varies significantly | High — rate is known and applied consistently |
Which Suits Which Type of Saver
Premium Bonds tend to suit:
- Savers who already max out ISA allowances and want another fully tax-free option
- Those who value 100% capital security beyond the FSCS £85,000 limit (e.g., holding sums over £85,000 in cash)
- Savers who enjoy the "lottery" element and are comfortable with a lower expected return in exchange for a small chance of a large prize
- Emergency funds where instant, penalty-free access without breaking a fixed term matters
A Cash ISA tends to suit:
- Savers focused on maximising expected, reliable return
- Anyone wanting to use up their annual ISA allowance efficiently
- Savers who want predictable growth for a specific goal with a known timeline (e.g., saving towards a house deposit within a set period)
- Additional-rate taxpayers who've already lost their Personal Savings Allowance and want certainty rather than relying on the "already tax-free" nature of Premium Bonds alone (since a Cash ISA is equally tax-free but with a guaranteed rate)
A Practical Middle Ground
Many savers use both: an ISA (Cash or Stocks & Shares) for the core of their savings where a reliable, tax-free, and often higher expected return matters, and Premium Bonds for an emergency fund or surplus cash beyond the FSCS £85,000 protection limit, where unlimited Treasury-backed security and instant access are valued more than maximising average return.
Given that both are tax-free, the decision genuinely comes down to risk appetite and what matters more: a known, steady outcome, or a fully tax-free entry into a monthly prize draw with a small chance of a very large win.
Frequently asked questions
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