A Perpetual Bond (also known as a 'Perp' or 'Consol') is a type of bond with no maturity date. Imagine lending money to a company or government and in return, they promise to pay you interest forever. That's a perpetual bond in a nutshell. The issuer never has to repay the principal (the original amount you lent them); they just service the debt by making regular coupon payments for as long as they exist. This makes them one of the most unusual instruments in the financial world. The most famous historical examples are the 'Consols' issued by the British government to finance the Napoleonic Wars in the 18th century, some of which were only fully redeemed in 2015! Today, they are most commonly issued by banks looking to bolster their long-term capital reserves. For an investor, buying a perpetual bond is less like making a loan and more like buying a permanent income stream.
The concept is surprisingly simple. You buy the bond, and as long as the issuer remains solvent, you receive a fixed coupon payment at regular intervals (e.g., annually or semi-annually) in perpetuity. Since there is no end date, the only way to get your initial investment back is to sell the bond to another investor on the secondary market. This unique structure makes its valuation highly sensitive to changes in prevailing interest rates. The theoretical value of a perpetual bond is calculated with a simple formula:
Let's say you own a perpetual bond that pays $50 in interest each year. If the current interest rate for similar-risk investments is 5%, your bond is worth $1000 ($50 / 0.05). But if interest rates rise to 8%, the value of your bond plummets to $625 ($50 / 0.08). Conversely, if rates fall to 2.5%, its value soars to $2000 ($50 / 0.025). This extreme price volatility is the defining feature of a perp and its greatest risk.
As the valuation formula shows, perpetual bonds have an incredibly long duration, which is a measure of a bond's sensitivity to interest rate risk. Because the payments stretch out to infinity, even a small change in market interest rates can cause a large swing in the bond's price. Investors who buy perps are making a significant bet that interest rates will remain stable or fall. If rates rise, they could face substantial capital losses.
This is the modern catch. Most perpetual bonds issued today are not truly perpetual. They almost always include a call provision, which gives the issuer the right, but not the obligation, to buy back the bond at a predetermined price (usually its face value) after a specific date (e.g., five or ten years after issuance). This creates a lopsided risk for the investor:
Like any bond, a perpetual bond carries the risk that the issuer will face financial trouble and default on its payments. With a traditional bond, you might recover some of your principal in a bankruptcy proceeding. With a perpetual bond, if the coupon payments stop, you may lose your entire investment, as there is no promise of principal repayment to fall back on. This makes a thorough analysis of the issuer's long-term financial health absolutely critical.
The father of value investing, Benjamin Graham, was famously skeptical of long-term bonds, viewing them as offering a limited upside (the coupon payments) with a significant downside from inflation and interest rate risk. A perpetual bond is the ultimate long-term bond and magnifies these risks. So, is there ever a case for them?
For the average investor, however, perpetual bonds are a dangerous game. Their performance is almost entirely dictated by the unpredictable path of future interest rates, and the call provisions heavily favor the issuer. They are specialized tools for sophisticated investors who have a deep understanding of credit analysis and the macroeconomic environment. For most people building wealth through a value-based approach, sticking to understandable businesses is a far more reliable path than speculating on the infinite horizon of a perpetual bond.