A Zero Coupon Bond Has One Cash Flow and It Arrives Last
Strip out the coupons and a bond becomes a single payment at a single date. That simplicity makes it the cleanest instrument in fixed income and the most violent.
One Payment, One Date
A zero coupon bond makes no periodic payments. It is bought at a discount to face value and pays that face value at maturity. All the return comes from the difference.
Buy a ten year zero at 610 and receive 1,000 in ten years. The implied annual return is about 5.1 percent, compounded, with no cash arriving until the end.
Savings bonds work this way, and so do Treasury bills at the short end. The long dated version in the United States market comes mostly from STRIPS, where a dealer separates an ordinary Treasury into its individual coupon payments and its principal payment, and sells each as a standalone zero.
The Reinvestment Problem Disappears
An ordinary bond quoting a 5 percent yield to maturity only delivers 5 percent if every coupon is reinvested at 5 percent. Rates move, so that almost never happens exactly.
A zero has nothing to reinvest. The quoted yield is the realised yield, guaranteed, provided the issuer pays and you hold to maturity.
A zero coupon bond is the only fixed income instrument whose promised return is the return you actually get. Everything else depends on conditions that have not happened yet.
That certainty is why zeros are the natural tool for funding a known future liability. A pension obligation due in fifteen years is matched precisely by a zero maturing in fifteen years, with no assumptions required.
Maximum Duration
Duration measures price sensitivity to interest rates. For a zero coupon bond, duration equals its time to maturity exactly, because there is only one cash flow and it sits at the end.
A coupon bond of the same maturity has shorter duration, since some cash arrives earlier. That makes the zero the most rate sensitive instrument available at any given maturity.
| Instrument, 20 year | Approximate duration | Price change if rates rise 1 percent |
|---|---|---|
| 6 percent coupon bond | About 12 | Roughly negative 12 percent |
| Zero coupon bond | 20 | Roughly negative 20 percent |
This cuts both ways with force. Long zeros produce spectacular gains when rates fall and severe losses when they rise. They are the purest available expression of a view on interest rates, which makes them a tool for hedging long liabilities and a way to lose a great deal of money quickly.
The Phantom Income Problem
Tax authorities treat the annual accretion of a zero toward par as interest income, taxable in the year it accrues, even though no cash was received.
An investor holding a zero in a taxable account therefore owes tax every year on money they will not see for a decade. This is called phantom income, and it is the reason taxable zeros are generally held inside retirement accounts. Municipal zeros avoid the problem where the interest is exempt.
Where They Are Used
Liability matching is the main institutional use: pensions and insurers with defined future obligations buy zeros that mature when the payments are due.
They also appear in structured products, where a zero guarantees return of principal while a small remaining amount buys options for upside. The zero does the safety and the options do the performance.
And they are a standard vehicle for anyone wanting maximum exposure to falling rates without leverage, since the duration is embedded in the instrument rather than borrowed.
The Bottom Line
A zero coupon bond compresses a bond into one payment on one date. That removes reinvestment risk and makes the promised yield the realised yield. It also produces the longest duration available, so the price swings hard on any rate move, and it generates taxable income years before any cash arrives. Precise, useful, and not remotely conservative despite carrying government credit.