Greenshoe Option Singapore
The over-allotment clause that lets underwriters stabilise a new listing’s price
A greenshoe option, formally called an over-allotment option, lets IPO underwriters sell up to an extra 15% of shares beyond the original offer size, then buy them back in the open market if the price falls after listing. It’s a built-in tool to stabilise a newly listed stock’s price in its first weeks of trading.
Not financial advice. All figures for educational reference only. Last updated: October 2026.
Key Takeaways
- A greenshoe option allows underwriters to sell up to roughly 15% more shares than the original IPO size, commonly borrowed from the company or major shareholders.
- If the share price falls after listing, underwriters can buy back shares in the open market to cover that over-allotment, which creates buying pressure that helps stabilise the price.
- If the price rises instead, underwriters can exercise the option to buy the extra shares from the company at the IPO price, locking in the arrangement without loss.
- The term comes from the Green Shoe Manufacturing Company, the first issuer in the US to use this mechanism in its 1960s IPO.
- SGX-listed IPOs, particularly larger Mainboard listings, commonly include an over-allotment clause in their prospectus.
What Is a Greenshoe Option?
When a company lists on an exchange, underwriters try to price the IPO so demand roughly matches supply. In practice, demand is uncertain, and a stock can trade below its IPO price in the first days if sentiment turns. The greenshoe option gives underwriters a tool to manage that risk: the right to sell additional shares, typically up to 15% more than the base offer size, usually borrowed from a major shareholder or the company itself.
If the stock trades down after listing, underwriters buy shares in the open market to cover that short position, shares they’d already sold through the over-allotment. That buying activity adds demand at a moment the stock needs it, helping cushion the price. If the stock instead trades up, underwriters simply exercise the greenshoe option, buying the extra shares from the company or shareholder at the original IPO price, and deliver them to the investors who bought the over-allotted shares.
How Does a Greenshoe Option Work in an SGX IPO?
The mechanism is spelled out in the IPO prospectus before listing. A company offering, say, 100 million new shares might also grant underwriters an option to over-allot up to 15 million additional shares (15%), sourced from an existing major shareholder willing to lend out shares for this purpose. The underwriters sell all 115 million shares to investors at the IPO price on listing day, effectively running a short position on the extra 15 million.
In the 30 days after listing (the typical stabilisation window), if the share price falls below the IPO price, underwriters buy back up to 15 million shares in the open market to cover the short position, supporting the price in the process. If the price instead stays above the IPO price, underwriters exercise the greenshoe option and buy the 15 million shares from the lending shareholder at the IPO price instead, with no need to intervene in the market.
Greenshoe Option Example
A company IPOs 200 million shares at $1.00 each on SGX, with underwriters granted a 15% greenshoe (30 million additional shares). On listing day, sentiment turns negative and the price slips to $0.92. Underwriters, who had already sold the full 230 million shares including the over-allotment, step into the market and buy back up to 30 million shares at prices around $0.92-$0.95, supporting the price and partially offsetting the decline, while covering their short position from the over-allotment.
Why the Greenshoe Option Matters to Investors
- Reduces early volatility. The stabilisation buying can smooth out sharp drops in the first weeks of trading.
- Signals underwriter confidence. A larger greenshoe allocation can suggest underwriters expect, or are prepared for, strong demand.
- Doesn’t cost the company extra. The shares used are typically borrowed from an existing shareholder, not newly issued at the company’s expense beyond the agreed terms.
- Disclosed upfront in the prospectus. Investors can see the maximum over-allotment size and stabilisation period before deciding to apply for an IPO.
Risks and Limitations
- Stabilisation isn’t guaranteed to work. If selling pressure overwhelms the greenshoe’s buying capacity, the price can still fall meaningfully.
- Temporary effect only. The stabilisation window is typically limited to around 30 days; price support disappears once it ends.
- Can mask genuine demand weakness. A stock propped up by greenshoe buying during the window may fall further once that support is withdrawn.
- Only available on IPOs that include the clause. Smaller Catalist listings don’t always carry a greenshoe option.
IPO With Greenshoe Option vs Without
| With Greenshoe Option | Without Greenshoe Option | |
|---|---|---|
| Price support after listing | Underwriters can buy back shares to stabilise price | No formal mechanism; price moves freely from day one |
| Typical allotment size | Up to 115% of the base offer | Exactly the base offer size |
| Underwriter flexibility | Can respond to demand swings in either direction | Fixed once listing is priced |
| Common on | Larger Mainboard IPOs | Smaller Catalist listings, though it varies |
Frequently Asked Questions
Why is it called a greenshoe option?
The name comes from the Green Shoe Manufacturing Company, the first issuer in the United States to include this over-allotment mechanism in its IPO in the 1960s. The term has since become the generic name for the clause across global markets, including Singapore.
Does a greenshoe option cost the IPO investor anything extra?
No. Investors who receive shares through the over-allotment pay the same IPO price as everyone else. The mechanism is a tool for underwriters to manage supply and price stability, not an extra charge to investors.
How long does the stabilisation period usually last?
It’s typically around 30 days from the listing date, though the exact window is set out in the specific IPO’s prospectus and stabilisation manager agreement.
Where do the extra shares in a greenshoe option come from?
They’re usually borrowed from an existing major shareholder who agrees to lend shares for the purpose, rather than being newly issued by the company specifically for this mechanism.
Do all SGX IPOs include a greenshoe option?
No. It’s common on larger Mainboard IPOs but not universal, and smaller Catalist board listings don’t always include the clause. Check the specific prospectus to confirm.