Amortized Bond

What Is an Amortized Bond?

An amortized bond is a debt security that repays its principal in gradual installments over its life instead of returning the full amount in a single payment at maturity. Each scheduled payment covers the interest owed on the remaining balance plus a portion of the original principal, so the outstanding amount shrinks with every payment until it reaches zero at the final due date.

The concept borrows from amortization in loan accounting. It is the same structure used in a typical fixed-rate mortgage, with the bond issuer acting as the borrower and the investor receiving both interest and principal back over time.

How It Works

In the early years, most of each payment is interest because the balance is still large. As principal is repaid, the balance falls, so the interest portion shrinks and the principal portion grows. The payment schedule is set when the bond is issued.

This differs from a bullet bond, which pays interest periodically and returns the entire principal at maturity. Some issuers instead use a sinking fund, setting aside money to retire part of a bond issue before the final date. Amortizing structures are also common in pools of loans, such as those underlying a mortgage-backed security.

Why It Matters to Investors

Because cash comes back gradually, an investor receives part of their money earlier than they would with a bullet bond. The cash arriving over time may need to be reinvested at prevailing rates, which introduces reinvestment risk. Because the average life of an amortizing bond is shorter than its final maturity date, its expected return is often described using a measure such as yield to maturity that accounts for the timing of each payment.

Accounting Note

The word "amortized" also appears in bookkeeping. When a bond is bought for more or less than its face value, the difference is spread over the remaining life of the bond, which gradually changes the recorded value of the holding. This is separate from the repayment structure described above, and the two uses are easily confused.