A zero-coupon convertible bond pays investors no interest at all, yet the company issuing it is still paying — just not in cash coupons. The real price is the equity conversion option the issuer sells alongside the debt: if the stock rises, bondholders convert and existing shareholders are diluted, and issuers routinely spend tens of millions of dollars up front hedging that exact risk. The structure has become the signature financing tool of the AI buildout. Reuters figures cited in a KuCoin recap of the 2026 convertible market put US-listed convertible issuance at roughly $131 billion through early September 2026, a record, with about half tied to AI projects such as data centers and chips — including zero-coupon deals from ON Semiconductor ($1.3 billion) and Ciena ($2.9 billion).
Table of Contents
- What a zero-coupon convertible actually is
- Where the cost hides when the coupon is zero
- The cash issuers spend to hedge their "free" money
- Why the income statement understates it
- What a shareholder should check in any zero-coupon AI deal
- Frequently Asked Questions
What a zero-coupon convertible actually is
A convertible bond is debt that the holder can swap for shares at a preset price. A zero-coupon convertible drops the interest payments entirely: the investor lends money, collects nothing along the way, and is repaid at maturity unless the stock climbs enough to make conversion the better deal. Why would anyone lend for free? Because the loan comes bundled with a call option on the stock.
Alibaba's September 2025 deal shows the mechanics: its roughly $3.2 billion of zero-coupon notes convert at 5.1773 ADSs per $1,000, an initial conversion price of $193.15 per ADS, so noteholders are compensated in potential equity upside rather than interest, per Alibaba's pricing release. The issuer, in other words, is selling two things at once: a bond and an option. The buyer pays a single price for the package, and the option's value is what substitutes for the missing coupon.
Where the cost hides when the coupon is zero
The Footnotes Analyst breaks the package apart: part of the issue price is really payment for the embedded conversion option, and once you strip that out, what remains is discounted debt. That discount accretes over the bond's life, producing an effective cost of debt comparable to a straight bond — about 3.25% in the worked example. The true cost of capital is the weighted average of the debt component and the option component.
For shareholders, the cost shows up as contingent dilution. If the stock beats the conversion price, the company effectively issues new shares at a price set today — below wherever the stock has climbed to. The financing was cheap only if the stock stagnates, which is not the outcome anyone issuing to fund an AI buildout is planning for.
The cash issuers spend to hedge their "free" money
The clearest proof that zero-coupon is not zero-cost is that issuers write real checks at closing to contain the dilution. Tempus AI priced an upsized $400 million of 0.00% notes due 2032 in May 2026, convertible at about $69.26 — a 40% premium to its stock price — and immediately spent approximately $27.2 million of the proceeds on capped call transactions with a cap price of $98.94, per the Tempus pricing announcement.
That is nearly 7% of the raise, paid on day one, on a bond that pays "nothing." A capped call is a bank-sold hedge that offsets dilution between the conversion price and a higher cap. Alibaba did the same thing, buying capped calls that effectively lift its conversion price to $235.46 per ADS, a 60% premium, according to its SEC filing. Above the cap, dilution resumes.
Why the income statement understates it
Under ASU 2020-06, US GAAP no longer requires splitting a convertible into a discounted debt piece and an equity piece. The whole bond sits on the books near face value, so reported interest expense on a zero-coupon convert can be close to zero.
The Footnotes Analyst warns this treatment inflates earnings and that analysts should reintroduce the economic financing cost themselves. The practical effect: two companies with identical economics can report very different interest expense depending on whether they issued straight debt or a zero-coupon convert. EPS comparisons across AI-infrastructure issuers are distorted unless you adjust.
What a shareholder should check in any zero-coupon AI deal
When a company you hold announces one of these deals, a few numbers tell you most of what matters: The scale matters too. With CoreWeave ($4 billion), Oracle ($5 billion), ON Semiconductor and Ciena all tapping the market in 2026, converts are now a primary channel for AI capital spending, and the aggregate dilution overhang is sector-wide, not company-specific.
- The conversion premium — Tempus set 40%, Alibaba's cap sits 60% above the pricing-date close. A low premium means dilution kicks in early.
- The capped call cost, if any — cash spent at closing is a direct reduction of net proceeds.
- Potential share count if fully converted, against the current float.
- What the money funds — Alibaba directed about 80% of net proceeds to cloud infrastructure, per its completion announcement; vague uses deserve more skepticism than named data-center commitments.
- Whether reported interest expense reflects the economics, given the ASU 2020-06 treatment above.
Frequently Asked Questions
Does the company ever pay cash on a zero-coupon convertible?
Yes — the principal is repaid at maturity if holders don't convert, and many issuers, like Tempus with its $27.2 million capped call purchase, pay hedging costs at issuance.
Is a zero-coupon convertible better for shareholders than a stock offering?
It defers dilution rather than avoiding it. Shares are only issued if the stock beats the conversion price, but then they're issued below the market price at that time.
Why does reported interest expense look so low on these bonds?
ASU 2020-06 lets US issuers book the whole convertible as debt without separating the option value, so accreted interest that older accounting would have shown largely disappears from the income statement.