What it means
Municipal issuers need a number to compare competing underwriter bids, and net interest cost provides the quick one: total interest dollars over the life, divided by the total bond-years. The arithmetic is deliberately simple: sum the coupon payments, adjust for any premium or discount, and divide by the sum of principal multiplied by years outstanding.
Bond-years carry the weighting, since a twenty-year issue's later maturities dominate the denominator, which is why payment structure moves NIC even at identical coupons. The flaw is built in.
NIC treats an interest payment in year twenty as equal to one in year one, ignoring the time value of money entirely. True interest cost is the sophisticated sibling, because TIC discounts the payment stream properly, and issuers awarding bids on NIC alone can choose the wrong winner when payment structures differ across bids.
The trap is structural, since bids that push interest later or front-load principal can game NIC downward while costing more in present value, which sophisticated issuers and advisers understand well. The Municipal Securities Rulemaking Board teaches the distinction, and its published guidance on competitive bidding explains how issuers evaluate bids, including the measures used to determine the winning offer.
NIC survives for good reasons: it is computable by hand, easy to explain to a board, and for plain-vanilla issues with similar structures it ranks bids the same way TIC does. Boards understand it instantly because it reads like an average rate, which is precisely its danger and its charm, familiarity without the discounting rigour underneath.
Modern practice runs both. Software computes TIC effortlessly, so NIC's remaining role is communication, not calculation, and policies increasingly name TIC as the award basis.
For a business owner issuing debt or comparing loan offers, the lesson generalises: any cost measure that ignores timing can be gamed by timing, so match the metric to the sophistication of the offer. Comparing loan offers by simple average cost invites the same gaming, and an internal-rate-of-return comparison is the private-sector TIC.
In practice
Real-world examples.
Example
A city awards bonds on NIC and later learns a discounting comparison would have picked the rival bid. The simpler measure picked wrongly.
Example
An adviser shows a board that NIC and TIC rank three identical-structure bids the same way, validating the simpler measure for that sale. Simple structures rank the same.
Example
A treasurer adds a TIC check to the NIC policy after an auditor flags the gaming risk in late-loaded payment structures. The audit changed the award rule. The auditor made the distinction stick.
Formula
Calculation
NIC = (total interest payments - premium + discount) / bond-years, where bond-years = the sum of principal outstanding x years outstanding.
Worked example. A $10 million issue repaid in one lump sum after 10 years has $10,000,000 x 10 = 100,000,000 dollar-years of borrowing. With total interest of $4,000,000, NIC = $4,000,000 / $100,000,000 = 4.0%, whatever the payment timing.
If the underwriter pays a premium of $200,000 for the bonds, NIC = ($4,000,000 - $200,000) / $100,000,000 = 3.8%.Case study
Seen in the real world.
In this illustrative fictional case, Ruth, finance director of a school district, receives two underwriter bids. Bid A wins on NIC but its payments cluster late; her adviser recomputes on true interest cost and Bid B wins by a meaningful margin. The board switches its award policy to TIC, with NIC reported alongside for transparency. In the recalculation, Bid A shows an NIC of 3.90% against 3.95% for Bid B, but a TIC of 4.12% against 4.04%. The policy now names both measures, and the award goes to the lower TIC.
Watch out
Common mistakes.
- Awarding complex deals on NIC alone, when structures that shift payments through time exploit its blindness to discounting, and TIC catches what NIC cannot. Discounting exposes the timing games.
- Assuming NIC and TIC always diverge, when plain structures rank identically under both, and the sophisticated measure costs nothing to compute today. Software removed the cost excuse.
- Comparing NIC across different maturities, when longer issues naturally carry different cost profiles, and only like-for-like structures make the comparison fair. Like-for-like is the only comparison.
Questions
People also ask.
What is net interest cost?
A bond issue's total interest cost divided by its bond-years outstanding, a simple average borrowing rate. It is widely used in municipal bid comparisons but ignores the time value of money. Bond-years do the weighting. Later maturities dominate the weighting. Speed is its remaining virtue.
How does it differ from true interest cost?
TIC discounts each payment to present value, while NIC treats all years equally. For similar structures they rank bids alike; for differing payment timing, only TIC identifies the cheaper bid. Timing is the entire difference. Structure games decide the winner.
Why is it still used?
Simplicity and tradition. It is computable by hand and easy to explain, and guidance from the Municipal Securities Rulemaking Board on competitive bidding helps issuers use both measures well. Communication is its surviving role. TIC now carries the award.
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