Index-Linked Gilts Explained: How UK Inflation-Protected Government Bonds Safeguard Your Purchasing Power

Index-linked gilts adjust both coupon payments and principal repayment in line with the Retail Prices Index (RPI). That single design choice separates them from every other fixed-income instrument available to UK investors.

Take the 0⅛% Index-linked Treasury Gilt 2039. The 0.125% coupon looks absurd next to a conventional gilt yielding 4.5%+. But that coupon is a real yield — it sits on top of whatever RPI inflation accrues between issue and payment. If RPI has risen 60% cumulatively since issue, your £1,000 nominal is treated as £1,600 for both coupon calculations and the principal you receive at maturity. The dirty price on this gilt is currently £110.94 per £100 nominal — that gap between clean price (£80.96) and dirty price reflects decades of accumulated inflation adjustment.

The indexation uses an 8-month lag for gilts issued before 2005 and a 3-month lag for newer issues. Payments don't respond instantly to inflation spikes. During the energy crisis of 2022-23, holders waited months for the uplift to feed through.

Crucially, index-linked gilts use RPI — not <a href="/posts/analysis-energy-price-cap-falls-7-in-april-what-it-means-for-your-household">CPI</a> or CPIH. According to the latest ONS consumer price inflation bulletin, RPI ran at 3.6% in February 2026 versus CPI at 3.0%. That 0.6 percentage point gap compounds significantly over a 20- or 30-year gilt. It also means index-linked gilts provide more inflation protection than headline CPI suggests.

For most of the 2010s, index-linked gilt real yields were negative. You were paying the government for the privilege of inflation protection. That era is over.

As of 4 April 2026, real yields from the UK index-linked gilt market tell a clear story:

• Short-dated (2027-2029): Still negative to barely positive — from -0.87% (2027) to +0.06% (2029)
• Medium-dated (2031-2038): 0.51% to 1.66% — the sweet spot for most investors
• Long-dated (2039-2055): 1.78% to 2.14% — highest real yields on the curve
• Ultra-long (2056-2073): 1.60% to 2.06% — yields dip slightly at the very long end

The 10-year benchmark (0⅛% IL Gilt 2036) yields 1.46% real. Buy today, hold to maturity, and you earn RPI inflation plus 1.46% annually — regardless of what happens to energy prices, Bank Rate, or geopolitics.

What drove this? The Bank of England cut Bank Rate from 5.25% to 3.75% between August 2023 and December 2025, but the Iran conflict upended that trajectory. Gilt yields spiked — the FRED long-term UK gilt yield series shows 4.43% for February 2026, up from 4.48% in December. For real yields, the conflict added roughly 80 basis points to UK borrowing costs across the curve.

A real yield of 1.5% compounding over 10 years adds 16% to your purchasing power beyond inflation. From a risk-free asset, that is genuine wealth-building territory.

The breakeven inflation rate tells you which gilt wins. It's the inflation rate at which an index-linked gilt and a conventional gilt of the same maturity deliver identical total returns.

With conventional 10-year gilts yielding roughly 4.8% and the equivalent index-linked gilt offering 1.46% real, the implied breakeven is around 3.3%. If RPI averages above 3.3% over the next decade, index-linked gilts win. Below that, conventional gilts win.

RPI currently sits at 3.6%. The <a href="/posts/deep-dive-how-boe-interest-rate-decisions-affect-your-finances">Bank of England</a>'s own forecasts don't see CPI returning sustainably to 2% before 2027 — and RPI runs structurally 0.5-0.8 percentage points higher than CPI due to the formula effect. The Iran conflict has injected fresh inflationary pressure through energy costs, with petrol and diesel seeing their largest monthly price rise on record in March 2026. You don't need to be an inflation hawk to think 3.3% average RPI over a decade is plausible.

Tax treatment favours index-linked gilts for higher-rate taxpayers. All gilts are exempt from capital gains tax — and with linkers, the inflation uplift on principal counts as a capital gain, not income. Only the (tiny) real coupon is taxed as income. Hold in an ISA or SIPP and even that disappears. For related guidance, see our ISA hub and tax planning hub.

Price volatility is the trade-off. Long-dated index-linked gilts are among the most volatile fixed-income instruments in sterling markets. The 0⅛% IL Gilt 2068 trades at just £48.90 per £100 nominal — its price has roughly halved from par. The 2073 maturity sits at £51.33. If real yields rise further, these prices fall further. Only buy long-dated linkers if you can hold to maturity or stomach significant mark-to-market swings.

For a broader view of how gilt yields feed through to mortgages and savings rates, see our gilt yields explainer.

Three routes to index-linked gilt exposure, each with different trade-offs.

Individual gilts via a broker. Hargreaves Lansdown, AJ Bell, interactive investor, and most UK stockbrokers let you buy specific index-linked gilts on the secondary market. You choose the maturity, lock in the real yield, and hold to redemption. Dealing fees run £5-12 per trade. This route gives you certainty — you know exactly what real return you earn if held to maturity. Be aware of the dirty price: the 0⅛% IL Gilt 2036 shows a clean price of £86.86 but you actually pay the dirty price of £135.89 per £100 nominal, which includes accrued inflation since issue.

The DMO Purchase and Sale Service. The UK Debt Management Office, administered by Computershare, allows approved investors to buy gilts directly. Slower and less convenient than a platform, but viable for buy-and-hold investors. For step-by-step instructions, see our practical gilt buying guide.

Index-linked gilt funds and ETFs. The iShares UK Index Linked Gilts <a href="/posts/investing-guide-index-funds-and-etfs-uk-low-cost-investing-for-beginners">ETF</a> and Vanguard UK Inflation-Linked Gilt Index Fund provide diversified exposure across maturities. The advantage: simplicity and liquidity. The disadvantage: no maturity date. A fund holds a rolling portfolio, so you never "lock in" a real yield — you're always exposed to changing real rates. In a rising-rate environment like 2025-26, fund investors have suffered capital losses even while underlying inflation protection worked as designed.

Tax wrappers matter. Gilts fit inside a Stocks & Shares ISA or SIPP. The CGT exemption already covers the inflation uplift on principal, so the main wrapper benefit is sheltering the income. For a 40% taxpayer holding £50,000 nominal of linkers outside a wrapper, the annual tax drag is modest — a few pounds on those tiny coupons — but it compounds over decades. Check our investing hub for platform fee comparisons.

Minimum investment is as low as one penny nominal, though platforms set practical minimums around £100.

The Iran conflict has reshaped the gilt market. The Strait of Hormuz closure on 2 March 2026 triggered the largest energy supply disruption in recorded history. Brent crude surged past $100, QatarEnergy declared force majeure, and UK gilt yields spiked harder than any other G7 economy's borrowing costs.

For index-linked gilt investors, this cuts both ways. Higher inflation expectations make the protection more valuable — RPI is likely to rise further as energy costs feed through to the March and April data (the next ONS release is due 22 April 2026). But higher real yields mean existing holdings have lost market value. If you already own long-dated linkers, you have felt the pain. Buying now, you are getting a much better deal than six months ago.

Three things to watch:

1. The BoE's next move. Markets had priced in rate cuts through 2026. The Iran shock paused that expectation. If the Bank holds at 3.75% or hikes, nominal gilt yields stay elevated — but real yields on linkers become even more attractive as the inflation premium grows. The Bank of England base rate has been unchanged since December 2025.

2. RPI reform in 2030. The government confirmed it will align RPI with CPIH from February 2030. For linkers maturing before 2030, this is irrelevant. For anything longer, your inflation measure switches from RPI (currently 3.6%) to CPIH (3.2%) — a permanent reduction in the uplift. The Supreme Court confirmed in 2022 that the government has legal authority to make this change. Price in the reform for any gilt maturing after 2030. Our gilts hub tracks the latest conventional and index-linked yields.

3. Fiscal pressures. The Iran conflict has blown a hole in the government's fiscal headroom. If borrowing rises, gilt supply increases, and yields could climb further. More supply of index-linked gilts specifically could push real yields even higher — good for new buyers, painful for existing holders.

Buy if: You are within 10-15 years of retirement and want to guarantee your pot keeps pace with living costs. A ladder of linkers maturing in sequence gives you inflation-proofed income without equity risk. At current real yields of 1.5%+, you are being paid handsomely. The debate between gilts at 5% vs savings accounts and the case against buying gilts is worth reading for both sides.

Buy if: You are a higher-rate taxpayer looking for tax-efficient fixed income. The CGT exemption on the inflation uplift makes linkers more efficient than corporate bonds or savings accounts where interest is fully taxed. Our savings hub compares after-tax alternatives.

Buy if: You genuinely believe inflation will stay elevated. With geopolitical conflict, energy disruption, and fiscal pressures, the arguments for persistent above-target inflation are stronger than they have been since the 1970s.

Don't buy if: You might need the money before maturity. Index-linked gilt prices swing violently — the 0⅛% IL Gilt 2068 is at £48.90, roughly half its par value. Selling early in a rising-rate environment crystallises real losses.

Don't buy if: You think inflation will collapse to 1-2% and stay there. In that scenario, conventional gilts yielding 4.8% will massively outperform, and you will have locked in a modest 1.5% real return when you could have had 3%+ nominal above actual inflation.

Don't buy if: You want simplicity. The RPI lag, the dirty/clean price distinction, and the 2030 reform make linkers genuinely complex. If that is off-putting, a diversified gilt fund handles the complexity for a small ongoing charge. For a broader look at bonds, see our how to buy bonds guide.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.