The Greenshoe Option
The greenshoe, formally the over-allotment option, lets the underwriters sell more shares than the company is offering and then decide, after trading has begun, where those extra shares come from.
It is the mechanism behind almost everything that happens to an IPO's price in its first month. An underwriter who has sold shares they do not yet own has a short position — and covering that short is either a purchase from the company or a purchase in the open market, depending on which direction the stock went.
How does the greenshoe work?
In three steps, the first of which happens before trading.
1. Over-allot. On a 100-million-share deal, the underwriters sell 115 million shares to investors at the offer price. They own 100 million. They are short 15 million.
2. Watch the aftermarket. The company has granted them an option to buy that extra 15 million at the offer price, less the underwriting discount, exercisable for a limited period after pricing.
3. Cover the short, one of two ways:
| If the stock | Underwriters | Effect |
|---|---|---|
| Trades above the offer price | Exercise the option and buy from the company | Company sells 15% more stock; underwriters earn the spread on it |
| Trades below the offer price | Buy in the open market instead | Buying supports the price; option expires unused |
Either way the short is covered and the underwriters are square. The choice is not a gamble — it is structurally profitable in both directions, which is the design.
Why is it called a greenshoe?
After the Green Shoe Manufacturing Company, whose 1963 IPO was the first to use the structure. The name stuck and the company's own name did not.
The company was founded in 1919. Those two dates are routinely conflated, including by sources that should know better; 1963 is the one that matters here.
How large can a greenshoe be?
Conventionally 15% of the base offering, and that convention has a regulatory edge to it.
FINRA Rule 5110 treats an over-allotment option greater than 15% of the base offering as unreasonable underwriting compensation. That is what makes 15% the near-universal ceiling rather than a coincidence of custom. Smaller options appear; larger ones do not.
The size is disclosed in the prospectus, in the underwriting section and on the cover.
How long does the greenshoe last?
Typically 30 days from the date of the final prospectus — but that number is a term of the offering, disclosed in the underwriting agreement and the prospectus, not a duration set by statute.
Read the specific deal rather than assuming. The window and the exercise conditions are written into each offering's documents and can differ.
What is the connection to price stabilisation?
The short position created by over-allotting is what makes aftermarket support possible at all.
When a newly listed stock trades below its offer price, the underwriters can buy in the open market to cover their short. Those purchases put a bid under the stock. Because the shares are being bought to cover a genuine short rather than to manipulate the price, the activity has an economic purpose beyond price support — though price support is unmistakably the effect.
This activity is governed by Regulation M, which permits certain stabilising transactions within defined limits and requires them to be disclosed. The three things to keep separate: FINRA Rule 5110 caps the option's size, Regulation M governs the stabilising activity, and the 30-day window is a contractual term.
See IPO stabilisation.
Are the underwriters ever genuinely short?
The distinction is worth drawing, because the two cases behave differently in a weak deal.
A covered short is the normal structure described above: the underwriters over-allot by no more than the greenshoe size, so the option covers the entire position whatever happens.
A naked short is where they over-allot beyond the option size. That excess can only be closed by buying in the open market, with no option to fall back on. It produces more aftermarket buying pressure if the stock is weak, and real exposure for the underwriters if the stock rises. Naked shorting in a distribution is constrained by Regulation M.
The standard structure is covered.
What happens if the greenshoe is exercised?
The company issues and sells the additional shares at the offer price less the discount, and the final deal size is larger than the headline.
This is why a deal's proceeds are frequently quoted two different ways, and why we always label which one we mean. Aramco's 2019 offering raised approximately $25.6 billion at pricing and approximately $29.4 billion after the over-allotment option was exercised. Alibaba's 2014 offering raised approximately $21.8 billion at pricing and approximately $25 billion after.
Both figures are correct for each deal. Mixing the two across a league table is how incorrect records get published.
See How is an IPO priced? · Methodology.
Are the greenshoe shares new shares or existing ones?
Either, and the prospectus says which.
Most commonly the option is granted by the company over newly issued shares, so exercise dilutes existing holders slightly and the proceeds go to the company. In some deals selling shareholders grant the option over their existing shares, in which case exercise is not dilutive and the proceeds go to them.
See Primary vs. secondary shares · IPO dilution.
Where does the greenshoe appear in the prospectus?
In three places, and they should agree.
The cover page states the base share count and the over-allotment shares, usually as a footnote to the price table. The Underwriting section sets out the option's size, exercise period and mechanics, and describes the stabilising activity the underwriters may undertake. The capitalisation and dilution tables show figures both assuming and not assuming exercise.
When a report cites a share count or proceeds figure that does not match the cover, the usual explanation is that one of the numbers assumes full exercise and the other does not.
See How to read an IPO prospectus · What is Form 424B4?.
Quick answers
Is the greenshoe exercised on most deals? It is exercised when the stock trades above the offer price, which describes most but not all debuts.
Does exercise dilute me? If the option is over newly issued shares, yes, modestly. If it is over selling shareholders' shares, no.
Is a greenshoe bad for investors? It is neutral by design. Exercise means the stock held up; non-exercise usually means the underwriters were supporting it.
Is 15% a legal maximum? FINRA Rule 5110 treats anything above 15% as unreasonable compensation, which functions as a ceiling.
Do direct listings have one? No. There is no underwritten allocation and therefore no over-allotment.
Related
IPO stabilisation · IPO underwriters · IPO underwriting fees · Offer price vs. opening price · How is an IPO priced? · How to read an IPO prospectus
Sources
- FINRA Rule 5110 — corporate financing rule, underwriting terms and arrangements
- Regulation M — stabilising transactions in connection with an offering
- Issuer final prospectuses on EDGAR — cover page and underwriting sections
- The IPO Radar filing and pricing database — Methodology