Cash ISAs at 4.5% Beat 3.3% Inflation Today — Index-Linked Gilts Make You Wait Years for a Worse Deal

March CPI landed at 3.3%, per the Office for National Statistics release on 22 April 2026. Motor fuels did most of the damage — the Iran war pushed pump prices up and that fed straight into the headline rate. Services inflation and core goods moved less.

The top easy-access cash ISA currently pays 4.51% AER, according to MoneySavingExpert's best cash ISA table. Fixed-rate cash ISAs reach 4.53% for one-year terms.

4.51% minus 3.3% is a real return of 1.21%. Tax-free. No duration risk. No maturity risk. No reinvestment risk. You keep access.

Now consider what an index-linked gilt actually offers. A 10-year index-linked gilt at current prices pays a real coupon measured in tenths of a percent, plus the RPI uplift on principal and coupon. RPI is structurally higher than CPI — typically 0.5–1.0 percentage points — so the headline real return looks reasonable. But you only capture that return if you hold to maturity, and you only hold to maturity if interest rates behave.

Index-linked gilts are long-duration instruments. The 2035 index-linked gilt has a modified duration above 8. Translation: a one-percentage-point rise in real yields knocks roughly 8% off the capital value overnight.

Real yields have whipsawed for four years. Sell an index-linked gilt into a 50 bps real-yield spike because you need the cash and you are crystallising a capital loss that no coupon will rebuild in five years. The Bank of England held Bank Rate at 3.75% on 18 December 2025 and the next MPC decision is 30 April 2026. If the committee surprises hawkish because of this CPI print, real yields rise — and your 'inflation protection' loses capital value on the day inflation fears are confirmed. That is the exact opposite of what buyers expect.

A cash ISA has a duration of zero. The capital value does not move when yields move. That matters more than the 0.3 or 0.5 percentage points of theoretical real-return pickup.

The Financial Services Compensation Scheme covers £85,000 per person per authorised deposit-taker. Two separately authorised providers and a joint account get you to £340,000 of deposit protection without touching the gilt market.

Index-linked gilts are direct UK government debt and carry gilt-edged credit risk (low). They do not carry FSCS deposit protection — they carry FSCS investment protection of £85,000 per person per failed firm if you hold them through a broker that collapses. That is a ceiling on firm-failure risk, not a ceiling on market risk. If the gilt price falls 12% because real yields moved, FSCS does nothing for you.

Cash ISAs are wrapped in the same £85,000 deposit guarantee and sit inside the £20,000 ISA allowance for 2026/27. Every penny of coupon is tax-free from day one. Gilts inside a General Investment Account attract income tax on coupons at your marginal rate — a 40% taxpayer loses 40% of the real coupon to HMRC. You can hold gilts inside a stocks and shares ISA to solve that, but then you are using ISA capacity on a lower-yielding, higher-risk asset than the cash ISA itself was offering.

The CPI headline is one print. The market reaction on 22 April was muted — gilt yields moved a handful of basis points. Traders are watching the 30 April MPC meeting, not the rear-view CPI release.

Three plausible paths:

1. MPC holds at 3.75% and signals patience — cash ISA rates hold at 4.5%, you earn 1.2% real. Your cash is fine.
2. MPC cuts 25 bps in May or June — cash ISA rates drift to 4.25%, you earn 0.95% real if CPI holds at 3.3%. Still positive.
3. MPC hikes because the committee panics about sticky services inflation — cash ISA rates rise toward 4.75%, real returns improve, and index-linked gilts sell off on the real-yield move.

In two of three paths the cash ISA wins or ties. In the hiking path, the cash ISA demolishes the index-linked gilt. The only scenario where index-linked gilts clearly win is sustained inflation reacceleration above 5% with stable or falling real yields — and that combination has not held for more than a few months in UK history.

This argument is the other side of a long-running debate. For the counter-case, read your cash savings are a melting ice cube on why some investors rotate into gilts when inflation is sticky. Our gilts at 4.75% guide covers the conventional-gilt alternative for people who want nominal certainty rather than inflation linkage.

For the ISA-first playbook, start with our best cash ISA rates for 2026/27 and our savings hub for fixed-rate bond comparison. If your marginal rate is above 20% and some of this capital is outside an ISA wrapper, our tax hub covers Personal Savings Allowance and the starting rate for savings — both of which change how much of your 4.5% you actually keep.

One more internal link worth surfacing: 4.75% cash savings, FSCS-protected is the longest-form version of the argument made here, with deeper historical comparison to the 1970s and early 1990s.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions. Rates and tax rules change — verify figures on the provider's website and gov.uk before acting.

Open a top-rate cash ISA before the 2026/27 allowance clock gets any further into the year. Split £20,000 between an easy-access ISA for emergency cash and a one-year fixed ISA for money you know you won't need. See our best cash ISA rates guide for current live rates and our cash ISA explainer hub for rules, transfers, and flexible-ISA mechanics.

Leave index-linked gilts to professional fund managers running pension liability portfolios. If you want inflation hedging inside an ISA, a small allocation to a diversified global equity tracker has outpaced RPI over every 10-year window in modern UK history — without the duration trap.

The one exception: you have a genuine long-dated liability that indexes to UK inflation — school fees over 15 years, a specific future purchase. A matching-maturity index-linked gilt held to maturity is defensible. For almost everyone else, it is a clever-sounding distraction from the boring answer that works.