Bonds — Lending Your Money

What a Bond Actually Is

A bond is a loan, dressed up in financial terminology that makes it sound more complicated than it is. You lend money to a government or a company. In exchange, the borrower agrees to pay you a fixed rate of interest — called the coupon — at regular intervals for a set period of time, and then return your original amount in full at the end, on a specific date called the maturity date.

Work through a concrete example. The UK government issues a bond — known in the UK as a gilt — with a face value of £1,000, a coupon of 4%, and a maturity of 10 years. You buy it for £1,000. Every year for the next ten years, you receive £40 in interest. At the end of the tenth year, you receive your original £1,000 back, in addition to all the interest payments already received. Across the full ten years, your total return is £400 in interest plus the return of your original £1,000 — assuming you hold the bond all the way to maturity and the borrower doesn't default.

The appeal of a bond, relative to a share, is predictability. You know, at the point of purchase, exactly how much interest you'll receive and exactly when you'll get your money back — assuming the borrower doesn't default. A share gives you no such guarantee about anything. This predictability is precisely why bonds are described, somewhat affectionately, as the reliable, unglamorous friend of the investing world: they rarely make headlines, and that is close to the entire point of holding them.

Why Governments and Companies Borrow This Way

Governments issue bonds to fund spending that exceeds what they raise through taxation in a given year — infrastructure projects, public services, emergency spending during a crisis, or simply managing the ordinary gap between annual tax revenue and annual spending commitments. Rather than printing money directly, which risks fuelling inflation, a government can borrow from investors — pension funds, insurance companies, other governments, and individual savers — promising a fixed return in exchange for the loan.

Companies issue bonds for a related but distinct reason: to raise money without diluting existing shareholders' ownership. Selling new shares raises cash but permanently gives new investors a claim on future profits and dilutes everyone else's percentage ownership. Issuing a bond raises cash too, but it creates a debt obligation rather than an ownership stake — the company must repay it with interest, but existing shareholders keep their full proportional ownership of the business. The trade-off: debt has to be serviced regardless of how the business performs, whereas a dividend to shareholders can be reduced or skipped in a difficult year without triggering a default.

This is also why bonds sit in a different position than shares if a company runs into serious financial trouble. Bondholders are creditors — they are owed a specific, contractually fixed amount — and in an insolvency, creditors are legally repaid before shareholders receive anything at all. This is a meaningfully different risk position from owning shares in the same company, and it's reflected in bonds' generally lower (though not zero) risk profile relative to equity in the same business.

A Short History of Why Gilts Are Called Gilts

UK government bonds are known as "gilts" — a name that dates back to the physical certificates originally issued by the Bank of England, which had gilt-edged borders, signalling the highest possible standard of financial reliability at the time. The term stuck long after the physical certificates themselves disappeared, and it's still used today purely as a name for UK government debt, in the same way "Treasuries" refers to US government debt and "Bunds" refers to German government debt.

Government borrowing through bonds long predates modern financial markets — the English government first issued long-term debt instruments in the late 17th century, partly to fund wars, establishing the principle that a government could borrow against its future tax revenue rather than only spending what it collected in a given year. This single innovation — the ability to smooth government spending over time by borrowing from investors who trusted the state to eventually repay through taxation — is one of the foundational mechanisms of the modern financial system, and it underpins the gilt market that still funds a significant portion of UK government spending today.

Modern gilts come in several forms worth knowing by name: conventional gilts, which pay a fixed coupon exactly as described earlier in this chapter; index-linked gilts, whose coupon and principal rise in line with inflation, covered in more detail later in this chapter; and Treasury bills, very short-dated instruments (typically under a year) used for the government's short-term cash management needs rather than long-term borrowing.

The Price-Yield Relationship (The Part That Confuses Everyone at First)

This is the single most counterintuitive idea in the entire bond market, and it trips up almost everyone the first time they encounter it: when bond prices rise, yields fall. When bond prices fall, yields rise. They move in permanently opposite directions, by mathematical necessity rather than coincidence.

Here's why, worked through carefully. Say you hold a bond paying a fixed £40 a year — the coupon never changes once the bond is issued, regardless of what happens afterward. If you originally paid £1,000 for it, your yield (return) is 4% (£40 ÷ £1,000). Now imagine interest rates across the wider economy rise, and newly issued bonds of similar risk start paying 5%. Your old bond, still only paying £40 a year, is now less attractive by comparison — nobody would pay you £1,000 for it when they could get a new bond paying £50 a year for the same price elsewhere. For your old bond to remain competitive, its price has to fall — to roughly £800 — so that the fixed £40 payment now represents a 5% yield on the new, lower price, matching what's available elsewhere in the market. The coupon payment itself never changes; only the price adjusts, to keep the yield in line with prevailing market rates.

This mechanism is precisely why bonds experienced one of their worst periods in decades during the rapid interest-rate-rising cycle of 2022, when central banks raised rates from near-zero to the 4–5% range in roughly eighteen months. Existing bonds, issued when rates were low, had to reprice sharply downward to remain competitive against newly issued bonds offering much higher coupons — a genuine, broad-based bond market decline that caught many investors who assumed bonds were simply "safe" off guard, since the safety of a government bond (near-certainty of repayment at maturity) is a different property from price stability before maturity.

Duration: Why Some Bonds Are Hit Harder Than Others

Duration is a measure of how sensitive a bond's price is to a change in interest rates, and it's closely related to how long the bond has left until maturity. As a rough rule of thumb, a bond with a duration of 10 years will fall in price by roughly 10% if interest rates rise by 1 percentage point, and rise by roughly 10% if rates fall by 1 percentage point. A bond with a duration of 2 years will move by roughly a fifth as much for the same rate change.

The intuition behind this is that a longer-dated bond locks in its fixed coupon for a much longer period, meaning it's exposed to a much longer stretch of time during which prevailing interest rates could move away from what the bond is paying. A short-dated bond maturing in six months will simply return your money very soon regardless of what rates do in the meantime, so its price barely moves in response to a rate change. A 30-year bond, by contrast, is locked into its fixed coupon for three decades, making its price highly sensitive to every shift in rate expectations over that entire period.

This is why investors specifically concerned about interest rate risk — those who may need to sell before maturity, or who hold bonds through a fund rather than individual bonds held to a fixed date — often favour shorter-duration bonds during periods when rates are expected to rise, accepting a somewhat lower yield in exchange for reduced price sensitivity.

Government Bonds vs Corporate Bonds

Within corporate bonds, there's a further important distinction: investment grade bonds (rated BBB- or above) are issued by companies considered to have a low risk of default, typically carrying a modest yield premium of perhaps 0.5–2 percentage points over equivalent government bonds. High-yield bonds — more commonly, if less flatteringly, known as junk bonds — are issued by companies with a meaningfully higher risk of default, and compensate investors with substantially higher yields, sometimes 4–8 percentage points or more above government bonds, reflecting the real possibility that some proportion of these borrowers won't fully repay.

It's worth being clear-eyed about what "junk" means here: it isn't a judgement that the bonds are worthless, but a statement about statistically elevated default risk relative to investment-grade borrowers. A diversified high-yield bond fund, holding many such bonds across different companies and industries, can be a reasonable component of a portfolio for investors comfortable with the additional risk and seeking higher income — but an individual junk bond, held alone, carries meaningful concentration risk in the same way an individual stock does.

Why Bonds Belong in a Portfolio

Bonds, particularly government bonds, have historically tended to move in the opposite direction to stocks during periods of acute market stress — when stock markets fall sharply amid fears of recession or crisis, investors often flee to the relative safety of government bonds, pushing bond prices up even as stock prices fall. This negative correlation, while not perfectly reliable in every single downturn, is what gives bonds their core value in a diversified portfolio — not simply their yield, but their role as a shock absorber during the periods when it matters most.

A classic "60/40" portfolio — 60% stocks, 40% bonds — has historically delivered a substantial majority of the long-run returns of an all-stock portfolio, while experiencing meaningfully lower volatility and smaller peak-to-trough declines during market crises. For investors who would otherwise panic-sell during a severe stock market downturn, the smoother ride offered by a meaningful bond allocation can be the difference between staying invested through a recovery and crystallising losses by selling at the bottom.

The Yield Curve and What It Signals

The yield curve is simply a chart plotting the yields of bonds from the same issuer (usually a government) across different maturities — from very short-dated (a few months) out to very long-dated (30 years). Under normal economic conditions, the curve slopes upward: longer-dated bonds pay higher yields than shorter-dated ones, because lending money for longer periods carries more uncertainty, and investors demand to be compensated for that additional uncertainty.

Occasionally, this relationship flips — short-term yields rise above long-term yields, producing what's called an inverted yield curve. This happens when markets expect interest rates to be cut in the future, which itself usually reflects an expectation of slowing economic growth or an outright recession ahead. An inverted yield curve has preceded most recessions in recent decades, though the lead time between inversion and an actual downturn has varied considerably, sometimes by well over a year, which limits its usefulness as a precise, actionable trading signal even though it remains a closely watched indicator among economists and market commentators.

For an ordinary long-term investor, the yield curve is more useful as a piece of background economic context than as a specific signal to act on. Attempting to restructure a portfolio every time the curve shifts shape tends to generate more in trading costs and mistimed decisions than it captures in benefit — it's a concept worth understanding, but not one that needs to drive frequent portfolio changes for most people.

How to Actually Access Bonds as a UK Investor

Direct purchase of individual UK government bonds (gilts) is possible through the UK Debt Management Office or through a broker, but for most retail investors this is more cumbersome than necessary, requiring you to manage individual maturity dates, reinvestment decisions, and a meaningfully larger amount of capital to achieve genuine diversification across multiple bonds and maturities.

For the large majority of UK investors, a bond ETF or index fund — holding gilts, global government bonds, or a mix of government and investment-grade corporate bonds — is the simplest and most practical way to add bond exposure to a portfolio, achieving broad diversification across issuers and maturities in a single purchase, and remaining fully compatible with a Stocks and Shares ISA.

Other Risks Worth Knowing About

Beyond default risk and interest rate risk, a handful of less-discussed risks are worth understanding before building a meaningful bond position, particularly if you're buying individual bonds rather than a diversified fund.

Callable bonds. Some corporate bonds include a "call" feature, allowing the issuer to repay the bond early, before its stated maturity date, usually if interest rates have fallen enough that the company can refinance more cheaply elsewhere. This is advantageous for the issuer and disadvantageous for you as the holder — you lose access to a now-attractive fixed coupon earlier than planned, and have to reinvest the returned capital at the new, lower prevailing rates. Callable bonds typically offer a slightly higher yield than otherwise-identical non-callable bonds specifically to compensate for this risk.

Currency risk on foreign bonds. A UK investor buying a US Treasury bond, priced and paid in dollars, is exposed to dollar-pound exchange rate movements in addition to the bond's own price and yield behaviour — a weakening dollar can erode returns in pound terms even if the bond itself performs exactly as expected in its own currency. Global bond funds often address this through currency hedging, which aims to neutralise this exchange rate effect, usually at a small additional cost reflected in the fund's fee.

Liquidity risk in smaller corporate bond issues. Large government bond markets are extremely liquid, with huge trading volumes and narrow gaps between buy and sell prices. Smaller corporate bond issues can be considerably less liquid, meaning that if you need to sell before maturity, you may only find a buyer at a less favourable price than the bond's theoretical fair value, particularly during periods of broader market stress when many holders are trying to sell simultaneously.

Reinvestment risk. If interest rates fall significantly by the time your bond matures, reinvesting the returned capital into a new bond will typically mean accepting a lower coupon than you were previously receiving — the flip side of the same mechanism that makes falling rates good news for a bond's price before maturity, but less good news for the income you can secure going forward after it matures.

A Worked Comparison: All-Stock vs 60/40 Through a Downturn

To make the diversification benefit concrete, consider two hypothetical £20,000 portfolios entering a severe market downturn in which stocks fall 35% over several months while government bonds rise 6% over the same period, reflecting the flight-to-safety pattern described earlier.

The 60/40 portfolio still falls — bonds reduce rather than eliminate downside risk — but the decline is roughly half as severe, which for many investors is the difference between tolerating the downturn and staying invested, versus panic-selling at the worst possible moment. The trade-off, evident in calmer markets, is that the 60/40 portfolio also tends to grow more slowly during sustained bull markets, since the bond allocation isn't participating in the stock gains during the good years either. This trade-off — smoother ride, somewhat lower long-run average return — is the central decision every investor makes when choosing a stock/bond allocation.

Bond Laddering: A Practical Income Strategy

For investors who want predictable, staggered access to their capital rather than locking everything into a single maturity date, bond laddering is a long-established and genuinely practical technique. Instead of buying one large bond maturing in ten years, you split the same total amount across several bonds with staggered maturities — say, one maturing each year for the next five years — and as each one matures, you reinvest the proceeds into a new bond at the far end of the ladder, extending it by one more year.

The benefit is twofold. First, you're never fully exposed to reinvesting your entire pot at whatever interest rate happens to prevail on a single specific day — your exposure to interest rate changes is spread across multiple reinvestment points over time, smoothing out the effect of being unlucky with timing. Second, a portion of your capital is always approaching maturity, giving you regular, planned access to cash without needing to sell any bond early at an uncertain market price.

Bond ladders are more commonly built by investors managing a retirement income need or a specific, staged savings goal, using individual bonds rather than funds, specifically because the known, fixed maturity dates are the whole point of the structure — a bond fund, as covered earlier, doesn't offer the same fixed-date certainty since it continuously rolls its holdings. For most people investing for general long-term growth rather than a staged income need, a simple diversified bond fund remains the more practical and lower-effort choice.

Using Bonds for Retirement Income

Bonds play a particularly important role for investors who have moved from building wealth during their working years to drawing an income from it in retirement. The fixed, predictable nature of coupon payments makes bonds a natural building block for generating reliable income to cover essential living costs, in a way that dividend income from shares — while often substantial — can't quite match in certainty, since dividends can be cut during a difficult year for a company in a way that a government bond's coupon simply cannot.

A common approach among retirees is to hold several years' worth of anticipated essential spending in short-to-medium-dated bonds or a bond ladder, specifically to avoid being forced to sell shares during a market downturn to cover day-to-day costs. This "bucket" approach — cash and short-dated bonds for near-term spending, a diversified bond allocation for medium-term stability, and stocks for long-term growth to outpace inflation over the remaining decades of retirement — lets a retiree ride out a stock market downturn without needing to touch the stock portion of the portfolio at all, giving it time to recover before it needs to be drawn down.

It's worth distinguishing this approach from buying an annuity, a financial product sold by an insurance company that converts a lump sum into a guaranteed income for life, in exchange for giving up access to the capital itself. An annuity and a bond ladder solve a similar underlying problem — converting savings into reliable income — but an annuity transfers both the investment risk and the risk of living longer than expected to the insurance company, at the cost of permanently losing access to the underlying capital, whereas a bond ladder keeps the capital under your own control throughout.

Common Misunderstandings About Bonds

Assuming "bonds" always means "safe" in every sense. Government bonds from stable economies carry very low default risk, but all bonds — government and corporate alike — carry interest rate risk, as the 2022 bond market decline demonstrated clearly. "Low default risk" and "stable price" are two different properties, and conflating them led many investors to be surprised by bond losses in recent years.

Treating a bond fund the same as an individual bond held to maturity. An individual bond held to maturity has a known, fixed repayment date and amount. A bond fund continuously buys and sells bonds to maintain a target maturity profile, meaning it never "matures" in the same sense — its value will fluctuate with interest rates indefinitely, for as long as you hold it, without ever returning to a guaranteed face value on a fixed date.

Ignoring credit rating differences within "corporate bonds" as a single category. The gap in risk between a AAA-rated blue-chip corporate bond and a CCC-rated distressed company's bond is enormous, even though both are technically "corporate bonds." Always check where a specific bond or bond fund sits on the credit spectrum before assuming a given yield is simply free extra income.

Underestimating inflation's effect on fixed coupon payments. A 4% coupon looks attractive when inflation is running at 2%, but considerably less attractive when inflation runs at 6% — your fixed interest payment buys progressively less in real terms each year, even though the pound amount you receive never changes. This is why some investors specifically add inflation-linked bonds, whose coupon and principal adjust with inflation, as a complement to conventional fixed-coupon bonds.