Comparison · Savings & Investing · 2026/27
Cash ISA vs Stocks and Shares ISA: Which is Right in 2026/27?
Both types of ISA share the same GBP 20,000 annual tax-free allowance in 2026/27, but they work very differently. A Cash ISA delivers a predictable, guaranteed return -- typically 3-5% AER from competitive providers -- with no risk of losing your capital. A Stocks and Shares ISA invests in the stock market and can generate significantly higher long-term growth, but your money can go down as well as up. This guide compares them on returns, risk, charges, flexibility, and protection so you can decide which is right for your goals.
2026/27 Key ISA Figures at a Glance
- Annual ISA allowance: GBP 20,000 (unchanged from 2025/26)
- Cash ISA -- typical easy-access rate: ~4.0-5.0% AER from top providers
- Cash ISA -- typical fixed-rate (1-2 yr): ~3.5-4.8% AER
- Stocks and Shares ISA -- historic global equity annualised return: ~7-10%/yr (not guaranteed)
- FSCS protection: GBP 85,000 per institution for both types
- Tax on growth inside any ISA: Zero -- no income tax, no capital gains tax
- Lifetime ISA sub-limit (within GBP 20k): GBP 4,000 + 25% government bonus
Side-by-Side Comparison
| Feature | Cash ISA | Stocks and Shares ISA |
|---|---|---|
| Returns potential | 3-5% AER (fixed or variable); guaranteed by provider | 7-10%/yr historical average; not guaranteed -- can be negative |
| Risk level | No capital risk -- guaranteed return of your money | Market risk -- value can fall below amount invested |
| Charges | None from most providers; rate is what you see | Platform fee 0.15-0.45%/yr + fund OCF 0.06-1.50%/yr |
| Flexibility | Easy-access: withdraw any time; fixed: early exit penalties may apply | Can sell investments and withdraw; settlement takes 1-3 days |
| FSCS protection | GBP 85,000 per institution -- covers deposits | GBP 85,000 per firm -- covers firm failure, NOT investment losses |
| Best for | Short-to-medium term goals (under 5 years); emergency fund; risk-averse savers | Long-term wealth building (5+ years); beating inflation; retirement savings |
| Tax treatment | All interest tax-free; no income tax; nothing to declare on tax return | All gains and income tax-free; no CGT on profits; no tax on dividends |
Cash ISA: Guaranteed Returns, Zero Capital Risk
A Cash ISA works like a standard savings account but with a crucial difference -- all interest is tax-free, no matter how much you earn. Without the ISA wrapper, basic-rate taxpayers can only receive GBP 1,000 of savings interest tax-free per year (the Personal Savings Allowance), while higher-rate taxpayers are limited to GBP 500. A Cash ISA removes this ceiling entirely, making it especially valuable for higher earners and those with larger cash balances.
In 2026/27, competitive easy-access Cash ISAs from online banks and building societies were offering around 4.0-5.0% AER. Fixed-rate Cash ISAs, where you lock money away for 1-3 years, were typically in the 3.5-4.8% range. These rates fluctuate with Bank of England base rate decisions, so a variable rate that looks good today may be lower in 12 months.
Pros of a Cash ISA
- Capital is 100% safe -- you will never receive back less than you put in
- FSCS protection up to GBP 85,000 per institution
- No platform or management charges -- the advertised rate is your return
- Easy-access options allow withdrawals whenever needed; flexible ISAs allow replacement in the same tax year
- Simple to understand -- no investment knowledge required
- Ideal for short-term goals such as a house deposit, car purchase, or emergency fund
Cons of a Cash ISA
- Returns are lower than long-term equity averages -- real purchasing power may erode over decades
- Fixed-rate accounts lock your money away -- early withdrawal penalties can be steep
- Variable rates change with the Bank of England base rate -- returns can drop at short notice
- Not well suited to long-term wealth accumulation goals on its own
Stocks and Shares ISA: Long-Term Growth, Market Risk
A Stocks and Shares ISA invests your money in assets such as shares, investment funds, bonds, or exchange-traded funds (ETFs). All growth, dividends, and gains inside the ISA are completely tax-free -- there is no capital gains tax (CGT) to pay when you sell, and dividends are not subject to income tax inside the wrapper. This is a significant advantage given that the annual CGT exempt amount outside an ISA was cut to GBP 3,000 in 2024/25.
Most financial planners recommend low-cost global index tracker funds for long-term ISA investing. A global all-world tracker fund with an OCF of around 0.10-0.20% and a platform fee of 0.15-0.45% gives broad diversification across thousands of companies at an all-in annual cost of under 0.65%. Historically, global equities have returned around 7-10% per year annualised over long periods -- but past performance is not a reliable guide to future results.
Pros of a Stocks and Shares ISA
- Higher long-term return potential than cash -- equities have historically beaten inflation and cash over 10+ year periods
- All gains and income are completely tax-free -- no CGT, no dividend tax, nothing to report
- Wide choice: index trackers, active funds, individual shares, bonds, ETFs, investment trusts
- Compounding over decades can produce substantially larger final sums than cash savings
- Monthly contributions reduce timing risk through pound-cost averaging
Cons of a Stocks and Shares ISA
- Capital is at risk -- your pot can fall in value, especially in the short term
- Annual charges (platform fee + fund OCF) reduce your return even in good years
- Requires an investment horizon of at least 5 years to reduce the risk of loss meaningfully
- Can be complex -- fund selection, asset allocation, and rebalancing require some research
- FSCS protection covers firm failure but NOT investment losses from market movements
Worked Example: GBP 10,000 Over 10 Years
Suppose you invest a lump sum of GBP 10,000 at the start of the 2026/27 tax year and leave it untouched for 10 years. The following three scenarios illustrate how the two ISA types might compare. All figures are illustrative -- returns are not guaranteed.
Scenario A -- Cash ISA, easy-access at 4.5% AER
GBP 10,000 at 4.5% AER compounded annually for 10 years gives approximately GBP 15,530. That is GBP 5,530 of tax-free interest -- guaranteed, regardless of what happens in markets. In practice rates will vary; variable rates track the Bank of England base rate and could fall. Locking into fixed-rate deals in chunks can help maintain a higher average rate over the decade.
Scenario B -- Stocks and Shares ISA, global tracker at 7% net of charges
GBP 10,000 growing at 7% per year net of charges for 10 years gives approximately GBP 19,670. That is GBP 9,670 of tax-free growth -- roughly GBP 4,140 more than the Cash ISA scenario. However, in any individual year the value could be up 25% or down 30%. The journey would be volatile; an investor who panicked and sold during a downturn could crystallise a loss. Long-term discipline is essential to achieving the long-run average.
Scenario C -- Stocks and Shares ISA, poor decade at 3% net of charges
Markets do not always deliver strong returns. A decade where global equities return only 3% net of charges gives approximately GBP 13,440 after 10 years -- meaningfully less than the Cash ISA at 4.5%. This illustrates the downside risk. History shows that poor decades do occur, particularly when markets are expensive at the point of investment. Diversification across geographies and asset classes (including some bonds) can moderate this risk.
| Scenario | Annual return | Value after 10 yrs | Tax-free gain |
|---|---|---|---|
| Cash ISA at 4.5% | 4.5% guaranteed | ~GBP 15,530 | GBP 5,530 |
| S&S ISA -- good decade (7%) | 7% net (not guaranteed) | ~GBP 19,670 | GBP 9,670 |
| S&S ISA -- poor decade (3%) | 3% net (not guaranteed) | ~GBP 13,440 | GBP 3,440 |
Illustrative only. Past performance is not a reliable indicator of future results. Inflation reduces the real purchasing power of all three outcomes. Charges for the S&S ISA scenarios are assumed already deducted from the net return figure.
Which Should You Choose?
The right answer depends on your time horizon, risk tolerance, and goals. A practical framework:
- Under 3 years: Cash ISA. You cannot afford a market downturn to wipe out a portion of a house deposit or planned expenditure at the wrong moment.
- 3-5 years: Borderline. A low-risk blended portfolio or fixed-rate Cash ISA could work, depending on your tolerance for potential losses.
- 5+ years (especially 10+): Stocks and Shares ISA has historically delivered better long-term outcomes, particularly via a low-cost global tracker. The longer the horizon, the lower the probability of ending up worse off than cash.
- Higher-rate or additional-rate taxpayer: The CGT and dividend tax savings from a Stocks and Shares ISA are especially valuable. Outside an ISA you pay 18-24% CGT on gains above GBP 3,000; inside it, nothing.
- Want simplicity and peace of mind: Cash ISA. No monitoring required, no volatility, predictable return.
Many savers hold both: a Cash ISA for the emergency fund and short-term goals, and a Stocks and Shares ISA for retirement or longer-term wealth building. Since April 2024, you can subscribe to both in the same tax year as long as the combined total stays within GBP 20,000. This hybrid approach is used by millions of UK savers and is perfectly valid under current ISA rules.
Conclusion
Cash ISAs and Stocks and Shares ISAs are complementary tools, not rivals. Use a Cash ISA for money you need certainty on -- your emergency fund, a deposit saving, or any goal within five years. Use a Stocks and Shares ISA for long-term goals where you can tolerate short-term volatility in exchange for higher expected growth. Both sit inside the same GBP 20,000 annual wrapper and both give you completely tax-free returns.
The biggest mistake is leaving money in a non-ISA savings account when rates are above the Personal Savings Allowance threshold -- or letting fear of markets keep long-term savings in cash when time is on your side. Use the GBP 20,000 allowance every year; it cannot be carried forward.