FAR Bond Amortization: Effective Interest Method Explained with Examples

The effective interest method calculates interest expense by multiplying the bond's current carrying value by the market (effective) interest rate at issuance. The difference between this interest expense and the cash interest paid (face value times stated rate) is the amortization amount for that period. The carrying value updates each period, which means interest expense changes each period -- unlike straight-line, which spreads the discount or premium evenly. This is the method GAAP requires and the one FAR tests.

#Key Points

• Interest Expense = Carrying Value x Market Rate; Cash Paid = Face Value x Stated Rate; Amortization = the difference
• Discount bonds: carrying value increases each period toward face value; interest expense exceeds cash paid
• Premium bonds: carrying value decreases each period toward face value; cash paid exceeds interest expense
• GAAP (ASC 835-30) requires the effective interest method unless straight-line produces materially similar results
• FAR tests bonds on both MCQs (single-period calculations) and TBS (full amortization schedules, journal entries)
• The most common exam errors involve using the wrong rate (stated vs. market) and forgetting to update carrying value

#What is the effective interest method?

The effective interest method is a way to amortize the difference between a bond's face value and its issuance price over the bond's life. It is grounded in three formulas:

Interest Expense = Carrying Value at Beginning of Period x Market Rate

Cash Interest Paid = Face Value x Stated Rate

Amortization Amount = Interest Expense - Cash Interest Paid (for discounts) or Cash Interest Paid - Interest Expense (for premiums)

The carrying value changes each period because the amortization amount is added to it (for discounts) or subtracted from it (for premiums). This means interest expense also changes each period, since it is a function of the updated carrying value.

#How does bond discount amortization work?

A bond is issued at a discount when its stated rate is lower than the market rate. Investors pay less than face value to compensate for the below-market coupon payments.

Worked example:

• Face value: $100,000
• Stated rate: 5% (annual, paid annually)
• Market rate: 6%
• Term: 5 years
• Issuance price: $95,788 (present value of cash flows at 6%)

The discount is $100,000 - $95,788 = $4,212. This discount is amortized over 5 years using the effective interest method.

Amortization schedule:

Key observations:

• Interest expense increases each period because the carrying value increases
• Cash paid stays constant at $5,000 every period (face value x stated rate)
• The amortization amount grows each period
• By period 5, the carrying value reaches exactly $100,000 (face value)

Journal entries -- Period 1:

Issuance:

Dr. Cash                          $95,788
Dr. Discount on Bonds Payable      $4,212
    Cr. Bonds Payable                       $100,000

First interest payment:

Dr. Interest Expense              $5,747
    Cr. Discount on Bonds Payable             $747
    Cr. Cash                                $5,000

The debit to Interest Expense is the carrying value times the market rate. The credit to Cash is the face value times the stated rate. The difference reduces the Discount on Bonds Payable, which increases the net carrying value of the bond.

#How does bond premium amortization work?

A bond is issued at a premium when its stated rate is higher than the market rate. Investors pay more than face value because the coupon payments exceed what the market requires.

Worked example:

• Face value: $100,000
• Stated rate: 5% (annual, paid annually)
• Market rate: 4%
• Term: 5 years
• Issuance price: $104,452 (present value of cash flows at 4%)

The premium is $104,452 - $100,000 = $4,452. This premium is amortized over 5 years.

Amortization schedule:

Key observations:

• Interest expense decreases each period because the carrying value decreases
• Cash paid remains $5,000 each period
• The amortization amount (premium reduction) grows each period
• Carrying value converges to $100,000 at maturity

Journal entries -- Period 1:

Issuance:

Dr. Cash                         $104,452
    Cr. Bonds Payable                       $100,000
    Cr. Premium on Bonds Payable              $4,452

First interest payment:

Dr. Interest Expense              $4,178
Dr. Premium on Bonds Payable        $822
    Cr. Cash                                $5,000

For premium bonds, Interest Expense is less than Cash Paid. The difference reduces the Premium on Bonds Payable, which decreases the carrying value toward face value.

#How does this compare to straight-line amortization?

Straight-line amortization divides the total discount or premium evenly across all periods. It is simpler but produces a constant interest expense each period rather than one that reflects the changing carrying value.

Using the discount example ($4,212 discount over 5 periods):

Straight-line amortization per period: $4,212 / 5 = $842.40. Interest expense per period: $5,000 + $842.40 = $5,842.40.

When is each method appropriate?

On the FAR exam, default to the effective interest method. If a question says "the company uses straight-line amortization," use straight-line. If the question is silent on method, use effective interest.

#What are the most common bond exam traps?

FAR questions on bonds are designed to test whether you understand the mechanics or are applying formulas by rote. Here are the traps that appear most frequently:

#How should you approach bond questions on FAR?

Follow this sequence when you encounter a bond question on the exam:

1. Identify the bond terms. Write down: face value, stated rate, market rate, term, payment frequency, and issuance price. If the issuance price is not given, you may need to calculate it using present value tables or a present value formula.

2. Determine discount or premium. If issuance price < face value, it is a discount. If issuance price > face value, it is a premium. If issuance price = face value, the bond was issued at par and no amortization is needed.

3. Set up the first period. Calculate:

   • Interest Expense = Carrying Value x Market Rate (adjust for semiannual if applicable)
   • Cash Paid = Face Value x Stated Rate (adjust for semiannual if applicable)
   • Amortization = the absolute difference

4. Update the carrying value. For discounts, add the amortization amount. For premiums, subtract it.

5. Repeat for the number of periods the question asks about. If the question asks for the carrying value at the end of Year 3, you need to calculate periods 1 through 3.

6. Check your answer against the direction rule. Discount bonds: carrying value should increase each period, interest expense should increase. Premium bonds: carrying value should decrease each period, interest expense should decrease. If your numbers move the wrong direction, you have a rate error.

7. For journal entry questions, use the framework:

   • Debit Interest Expense (always the carrying value x market rate amount)
   • Credit Cash (always the face value x stated rate amount)
   • The plug goes to Discount or Premium on Bonds Payable

This sequence works for both MCQs and TBS. On MCQs, you may only need steps 1-3. On TBS, you may need the full schedule.

#How do bond issuance costs affect the calculation?

Under ASC 835-30, bond issuance costs (legal fees, underwriting fees, printing costs) are presented as a direct deduction from the carrying amount of the bond liability. They are not recorded as a separate asset.

Example: A company issues a $100,000 bond at $95,788 (discount) and incurs $2,000 in issuance costs.

• Carrying value at issuance: $95,788 - $2,000 = $93,788
• The $2,000 issuance costs are amortized over the bond's life using the effective interest method, alongside the original discount
• The effective interest rate used for the combined amortization will be slightly higher than the 6% market rate because the company received less cash but owes the same face value

On the exam, bond issuance cost questions typically appear as a separate MCQ or as an additional requirement within a TBS. The key rule: issuance costs reduce the carrying value of the liability and are not a deferred charge or asset.

#Putting it together

Bond amortization under the effective interest method follows a mechanical process: compute interest expense using the market rate on carrying value, compute cash paid using the stated rate on face value, take the difference as amortization, and update the carrying value. The process repeats each period until the carrying value equals face value at maturity.

The method is testable because it requires precision -- using the wrong rate, forgetting to update the carrying value, or mishandling semiannual periods will produce an answer that matches one of the wrong answer choices. The exam is designed this way intentionally.

Build your amortization schedule practice around full tables, not single-period calculations. If you can construct a 5-period schedule from scratch without errors, single-period MCQs become straightforward. For broader FAR practice strategies, see FAR Practice Questions Strategy. For a walkthrough of another high-weight FAR topic, see FAR Consolidations Step by Step. And for the complete FAR preparation framework, see How to Pass FAR.