Premium Bonds vs Cash ISA: Which Is Better?
Two of the UK's most popular tax-efficient savings options, but they work very differently. Premium Bonds offer prize draws; Cash ISAs offer guaranteed returns. The right choice depends on your tax band and how much you're saving.
The Quick Answer
Cash ISA is better for most people saving under £30,000 — you get guaranteed, tax-free returns. Premium Bonds become more competitive with larger holdings and for higher/additional-rate taxpayers who've used their savings allowance. For additional-rate taxpayers, Premium Bonds are usually the winner due to their fully tax-free status and no impact on your ISA allowance.
Premium Bonds vs Cash ISA at a Glance
| Feature | Premium Bonds | Cash ISA |
|---|---|---|
| Provider | NS&I (government-backed) | Banks, building societies |
| Return type | Prize draw (chance-based) | Guaranteed interest rate |
| Current rate | 4.0% prize fund rate | 4.0–5.0% (best buys, 2026) |
| Tax on returns | Completely tax-free | Tax-free (within ISA wrapper) |
| Annual limit | £50,000 total holding | £20,000/year ISA allowance |
| Access | Instant (takes 1–3 working days) | Instant or notice period |
| Minimum investment | £25 | Varies (often £1) |
| Risk to capital | None (government-backed) | FSCS protected to £85,000 |
| Guaranteed return | No — you might win nothing | Yes — fixed or variable rate |
Expected Returns by Amount
Premium Bond returns are averages — your actual prizes will vary. Cash ISA returns are guaranteed at the stated rate. Here's how they compare at different holding levels:
| Amount Saved | Premium Bonds (avg/year) | Cash ISA at 4.5% |
|---|---|---|
| £1,000 | ~£40 (but likely £0–£75) | £45 |
| £5,000 | ~£200 (variable) | £225 |
| £10,000 | ~£400 | £450 |
| £20,000 | ~£800 | £900 |
| £50,000 (max) | ~£2,000 | N/A (exceeds ISA limit) |
Premium Bond figures assume the 4.0% prize fund rate and average luck. In practice, small holdings often win nothing for months.
Tax Treatment: Why It Matters
This is where Premium Bonds gain their edge for wealthier savers:
| Tax Band | Personal Savings Allowance | Best Option |
|---|---|---|
| Basic rate (20%) | £1,000 | Cash ISA usually (PSA covers most interest) |
| Higher rate (40%) | £500 | Depends on savings amount — Premium Bonds if PSA used |
| Additional rate (45%) | £0 | Premium Bonds usually win (everything is tax-free) |
Check your savings tax position with our Savings Tax Calculator.
Pros and Cons
Premium Bonds
- Completely tax-free prizes
- 100% government-backed
- Chance to win £1 million
- Doesn't use ISA allowance
- No guaranteed return
- Small holdings may win nothing
Cash ISA
- Guaranteed interest rate
- Predictable returns
- FSCS protected up to £85,000
- Wide choice of providers
- Uses £20,000 annual ISA allowance
- May need to switch for best rates
The Best Strategy: Use Both
For many savers, the optimal approach is to use both:
- Max out your ISA allowance first — £20,000/year of guaranteed, tax-free returns.
- Then add Premium Bonds — Up to £50,000 of additional tax-free savings outside your ISA.
- Keep an emergency fund in easy-access savings — 3–6 months of expenses you can access immediately.
This gives you up to £70,000 in tax-free savings (ISA + Premium Bonds) before touching taxable accounts. Use our ISA Calculator and Savings Calculator to plan your savings strategy.
Premium Bonds vs ISA FAQs
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