What Is Unamortized Bond Premium?

An unamortized bond premium refers to the difference between a bond's face value and its sale price. If a bond is sold at a discount, for instance, at 90 cents on the dollar, the issuer must still repay the full 100 cents of face value at par. Since this interest amount has not yet been paid to bondholders, it is a liability for the issuer.

Understanding Unamortized Bond Premium

The bond premium is the excess amount that the bond is priced at over its face value. When prevailing interest rates in the economy decrease, the price of bonds increase. This is because the market interest rate becomes lower than the fixed coupon rate on outstanding bonds.

Since bondholders are holding higher-interest paying bonds, they require a premium as compensation in the market. The unamortized bond premium is what remains of the bond premium that the issuer has not yet written off as an interest expense.

For example, let’s assume that when interest rates were 5% a bond issuer sold bonds with a 5% fixed coupon to be paid annually. After a period of time, interest rates declined to 4%. New bond issuers will issue bonds with the lower interest rate. Investors who would rather buy a bond with a higher coupon will have to pay a premium to the higher-coupon bondholders to incentivize them to sell their bonds. In this case, if the bond’s face value is $1,000 and the bond sells for $1,090 after interest rates decline, the difference between the selling price and par value is the unamortized bond premium ($90).

The unamortized bond premium is the part of the bond premium that will be amortized (written off) against expenses in the future. The amortized amount of this bond is credited as an interest expense. If the bond pays taxable interest, the bondholder can choose to amortize the premium, that is, use a part of the premium to reduce the amount of interest income included for taxes.

Special Considerations

Those who invest in taxable premium bonds typically benefit from amortizing the premium, because the amount amortized can be used to offset the interest income from the bond, which will reduce the amount of taxable income the investor will have to pay with respect to the bond. The cost basis of the taxable bond is reduced by the amount of premium amortized each year.

In a case wherein the bond pays tax-exempt interest, the bond investor must amortize the bond premium. Although this amortized amount is not deductible in determining taxable income, the taxpayer must reduce his or her basis in the bond by the amortization for the year. An unamortized bond premium is booked as a liability to the bond issuer. On an issuers balance sheet, this item is recorded in a special account called the Unamortized Bond Premium Account. This account recognizes the remaining amount of bond premium that the bond issuer has not yet amortized or charged off to interest expense over the life of the bond.

Example: Unamortized Bond Premium Calculation

To calculate the amount to be amortized for the tax year, the bond price is multiplied by the yield to maturity (YTM), the result of which is subtracted from the coupon rate of the bond. Using the example above, the yield to maturity is 4%.

• Multiplying the selling price of the bond by the YTM yields $1,090 x 4% = $43.60.
• This value when subtracted from the coupon amount (5% coupon rate x $1,000 par value = $50) results in $50 - $43.60 = $6.40, which is the amortizable amount.
• For tax purposes, a bondholder can reduce his or her $50 interest income to $50 - $6.40 = $43.60.
• The unamortized premium after a year is $90 bond premium - $6.40 amortized amount = $83.60.
• For the second tax year, $6.40 of the bond premium has already been amortized, so the bond's cost basis is $1,090 - $6.40 = $1,083.60.
• Premium amortization for Year 2 = $50 - ($1,083.60 x 4%) = $50 - $43.34 = $6.64.
• Premium remaining after the second year or the unamortized premium is $83.60 - $6.64 = $76.96.

Assuming the bond matures in five years, you can run the same calculation for the remaining three years. For instance, the bond's cost basis in the third year will be $1,083.60 - $6.64 = $1,076.96.