How Much Extra Bond Income Repays the Cost of Switching?

A replacement decision involves two transactions

FINRA describes markups and markdowns as possible dealer compensation in bond transactions. For someone replacing an existing bond, the relevant cash ledger includes the old position's sale proceeds and the new position's acquisition debit. A higher indicated yield on the replacement does not tell us how much capital survives both trades. Comparing two midpoint valuations can hide the amount consumed before the new investment starts earning.

The following exercise isolates that implementation hurdle. It deliberately assumes equal face amounts, regular coupon dates and no purchased accrued interest. It also assumes the two positions retain equal future clean values, except where a stress is introduced. These are restrictive assumptions used to make the cost boundary visible; real bond replacements can change credit exposure, maturity, optionality and the timing of every payment.

Supporting references: 1. FINRA: Bonds

Translate two dealer prices into a capital gap

An investor holds USD 25,000 face of bond A, carried at a hypothetical reference clean value of USD 25,000. An executable dealer bid of 99.20 returns USD 24,800. Bond B has the same USD 25,000 reference value, but its executable ask of 100.40 costs USD 25,100. Buying the same face amount therefore requires USD 300 of additional cash. Relative to the common reference values, that is USD 200 lost on sale plus USD 100 paid on entry.

The USD 300 is already embedded in these transaction prices. Do not subtract it again as an extra spread charge. If the investor is charged a separate commission, include that actual additional debit once. Likewise, a reference valuation may be useful for attribution without being a price the investor could obtain. The accounting must distinguish an analytical benchmark from an available bid or ask.

Calculate the income needed to recover the hurdle

Assume B pays USD 125 more annual coupon cash than A on the same face amount. Treat that increment as a supplied contractual difference, not as a maturity-yield estimate. With unchanged relative exit values, no reinvestment and no other costs, the cumulative extra cash is USD 125 after one year, USD 250 after two and USD 375 after three. Subtract the USD 300 implementation gap to obtain the table's net advantage.

The resulting cases are minus USD 175, minus USD 50 and plus USD 75. Dividing USD 300 by USD 125 gives a straight-line recovery time of 2.4 years. That is an economic approximation because annual coupons arrive on discrete dates; in the stated year-end schedule, cumulative receipts first exceed the hurdle at the third payment. The decimal boundary does not promise that money is received continuously throughout year three.

Stress the comparison with a relative price decline

Now suppose B's sale proceeds after three years are USD 500 lower than A's, in addition to the original implementation cost. The USD 75 apparent advantage turns into a USD 425 disadvantage. Extra coupon receipts have not insulated the holder from relative repricing. A spread widening, change in credit outlook or liquidity deterioration can overwhelm years of a modest income increment.

The decision boundary becomes USD 300 plus any expected relative exit disadvantage, all divided by the annual extra cash under a straight-line approximation. A future exit advantage would reduce the hurdle, but assuming one without evidence converts a cost comparison into a price forecast. If maturities or call dates differ, even that simple expression may fail because the positions no longer deliver comparable terminal claims.

The no-top-up case changes the face amount

An investor who refuses to add USD 300 cannot simply buy USD 25,000 face of B. Ignoring trade increments, the USD 24,800 sale proceeds purchase only about USD 24,701.20 face at an ask of 100.40. That smaller face amount changes coupon dollars and final repayment. Comparing its income with the old USD 25,000 position requires a new calculation; the USD 125 equal-face increment no longer applies automatically.

This distinction matters whenever a platform presents a switch as self-financing. Ask whether the comparison holds face value, market exposure or cash outlay constant. Each version can be legitimate, but the result answers a different question. A chart showing a higher yield while quietly reducing face amount can obscure a lower eventual principal payment. Retain an explicit cash line for the difference rather than assuming all value remains invested.

Evaluate the hurdle alongside what actually changes

FINRA's due-diligence guidance highlights maturity, call status and credit characteristics. Here they matter because an attractive implementation break-even calculation cannot establish that two bonds are suitable substitutes. A higher coupon associated with weaker payment prospects may deserve a completely separate credit assessment. A replacement that helps meet a dated liability could also be useful despite failing the narrow income-only hurdle.

Use the exercise when the purpose of switching is additional cash income over a specified period. Record executable prices, separately billed costs, face amounts and the intended exit assumption. If the planned horizon ends before enough incremental cash arrives, some other benefit must justify the transaction. That benefit should be stated and tested explicitly; it should not be smuggled into the calculation by labeling the extra coupon a guaranteed superior return.

Supporting references: 2. FINRA: Bond Investing and Due Diligence

Limits of this analysis

• Equal reference and exit values deliberately isolate implementation cost.
• Coupon increment is not a quoted yield spread or a complete valuation comparison.
• Actual trade sizes, accrued interest and changing risk can alter the result.