Quick Answer

IPO shares are not sold on a first-come, first-served basis. Before a stock ever trades publicly, its shares are distributed through a tightly controlled hierarchy: the issuing company and its lead underwriters set the offering size and price, build an order book dominated by institutional investors, and then allocate whatever remains down through broker-dealers to approved retail channels. Because the share count is fixed by the issuer while demand is effectively unlimited, it is the underwriters - not investors - who decide who receives an allocation. When an offering is oversubscribed, retail demand is usually the first thing scaled back.

The SpaceX (SPCX) IPO on June 12, 2026 made this concrete: roughly $250 billion in investor demand chased about $75 billion in available supply [1], and retail participation was cut across the board even as headline demand hit record levels. The structural lesson that applies to every IPO: aggregating demand is not the same as securing supply.

First, the Distinction Most Retail Investors Miss

Once a company is publicly listed, the rules are simple. Anyone willing to pay the market price can buy the stock through almost any brokerage or trading platform. Supply and demand meet continuously on the open market.

IPO allocation works in the opposite way. Before trading begins, the shares being sold in the offering are distributed through a private, gatekept process. This is the primary market - the one-time sale of new shares from the company to an initial set of buyers. The continuous trading that everyone sees afterward is the secondary market.

The confusion that costs retail investors is treating an IPO subscription as if it were a secondary-market purchase. It isn't. Submitting an order does not buy you shares; it requests an allocation from a fixed pool that someone else controls.

The IPO Allocation Hierarchy: Who Actually Decides

IPO shares move through a defined chain, and each layer has less discretion than the one above it:

1. The issuer. The company going public sets, with its bankers, how many shares to sell and at what price range. This caps total supply. Nothing downstream can increase it.
2. Lead underwriters (bookrunners). The investment banks managing the offering - the names you see on the cover of the prospectus - control the allocation. They run the roadshow, gather demand, set the final price, and decide which buyers receive shares.
3. Institutional investors. Mutual funds, pension funds, sovereign wealth funds, and hedge funds receive priority. Underwriters favor large, long-term holders because they help stabilize the stock after listing rather than flipping it on day one.
4. Broker-dealers and approved retail channels. Whatever is left flows to registered broker-dealers, who in turn distribute to eligible retail investors - often a small, capped slice of the deal.

The critical point is that discretion lives at the top. The issuer and its underwriters decide the size of the pie and how it is sliced. Everyone below them receives what is passed down.

How the Order Book Gets Built

In the weeks before pricing, underwriters run a book-building process. Management and the banks present to prospective investors during a roadshow, and investors respond with indications of interest - non-binding signals of how many shares they would buy and at what price.

The underwriters use this book to do two things: set the final offering price the night before trading begins, and decide allocations. Because a successful debut depends on the stock trading well after listing, underwriters allocate to buyers they believe will hold rather than immediately sell. That preference systematically advantages institutions over retail.

This is why a "huge" book is not good news for a retail subscriber. A heavily oversubscribed book gives underwriters more buyers to choose from - and more reason to prioritize the accounts that matter most to them.

Why Oversubscription Squeezes Out Retail

An offering is oversubscribed when investors collectively request more shares than exist. In high-profile IPOs this is the norm, not the exception, and the imbalance can be extreme.

SpaceX is a clean illustration. With roughly $250 billion of demand against $75 billion of supply [1], the deal was oversubscribed by more than three times. Even an unusually generous retail carve-out - about 30% of the raise, near $15 billion, went to retail [1], far above the typical single-digit percentage - could not satisfy that demand. Orders were scaled back, and many investors who requested shares received only a fraction or none.

When supply is fixed and demand is several times larger, rationing is not a glitch. It is the mathematically guaranteed outcome of the process.

Why Demand Doesn't Guarantee Supply

This is the structural insight beneath every IPO allocation story, and it is worth stating plainly.

Demand is elastic. Supply is fixed. Marketing, distribution networks, and onboarding tools can aggregate enormous demand quickly and globally. None of that activity creates a single additional share. The number of shares is set by the issuer at the top of the chain and cannot be expanded by interest further down it.

That has a direct consequence for any platform or broker that offers IPO access: its ability to deliver shares depends entirely on the allocation it receives from upstream. A channel can be excellent at attracting subscribers and still end up with little to distribute, because it sits at the bottom of a chain it does not control. If the intermediaries above it receive limited allocations, the channel receives even less.

In other words, organizing demand is the easy part. Securing supply - an actual allocation from underwriters - is the hard part, and it is decided long before most retail investors ever click "subscribe."

What This Means for Global Retail Investors

For investors outside the major financial centers, the practical takeaway is twofold.

First, primary-market access is structurally scarce. Most retail investors worldwide have no direct path to an IPO allocation; they participate, if at all, through a channel that has secured supply on their behalf.

Second, how a platform sources its shares matters more than how loudly it markets access. When evaluating any IPO-access product, the question is not "how many people can subscribe" but "where does this platform sit in the allocation chain, and what supply has it actually secured." A platform that builds direct relationships with the institutions that hold allocations is structurally better positioned than one that can only aggregate orders.

BitMart approaches primary-market access through IPOPrime, its platform for IPO-linked offerings. As the broader tech IPO pipeline develops, the same structural rules covered here will apply to every new listing.

Frequently Asked Questions

Can retail investors buy IPO shares at the offering price? Sometimes, but access is limited and not guaranteed. IPO shares at the offering price are allocated by underwriters, who prioritize institutional investors. Retail investors usually access the offering price only through a broker or platform that has secured an allocation, and even then receive a capped amount. Most retail buying happens on the secondary market after listing, at the prevailing market price.

What does "oversubscribed" mean? An IPO is oversubscribed when investors request more shares than the company is offering. The more oversubscribed a deal is, the smaller each subscriber's allocation tends to be - and the more discretion underwriters have over who gets shares at all.

Who decides who gets IPO shares? The lead underwriters managing the offering. They build the order book, set the final price, and allocate shares, generally favoring large institutional buyers expected to hold the stock rather than sell immediately.

Why did I only get a few shares - or none - when I requested more? Because the offering was oversubscribed and the available supply was rationed. When total demand exceeds the fixed number of shares, allocations are scaled back. Retail requests are typically reduced before institutional ones. Receiving a partial allocation or none is a normal result of a heavily oversubscribed IPO, not an error.

Does heavy IPO demand mean the stock will go up? Not reliably. Strong demand can drive a first-day price increase, but a large first-day move reflects supply-demand imbalance, not long-term value, and is not predictive of medium-term returns.

Key Takeaways

• IPO shares are allocated through a controlled hierarchy - issuer to underwriters to institutions to broker-dealers to retail - not sold first-come, first-served.
• Total supply is fixed by the issuer and cannot be expanded by demand further down the chain.
• Underwriters control allocation and prioritize long-term institutional holders, which structurally disadvantages retail.
• In an oversubscribed IPO, rationing is mathematically guaranteed; retail allocations are scaled back first.
• SpaceX (June 12, 2026) saw roughly $250B in demand against $75B in supply; even a ~30% retail carve-out could not meet demand.
• The decisive question for any IPO-access platform is where it sits in the allocation chain and what supply it has actually secured - not how much demand it can attract.

Risk Warning: Investing in IPOs and newly listed securities involves significant risk, including price volatility and the possibility of loss. IPO allocations are not guaranteed, and first-day price performance does not predict future returns. This content is for educational purposes only and does not constitute financial, investment, or legal advice. Always conduct your own research and consider your risk tolerance before investing.

References

[1] SpaceX Raises $75 Billion in Record-Setting IPO Ahead of Nasdaq Debut - CNBC - https://www.cnbc.com/2026/06/11/spacex-raises-75-billion-in-record-setting-ipo-ahead-of-nasdaq-debut.html

[2] SpaceX IPO Takeaways: SPCX Closes at $161, Jumping 19% After Record Debut - CNBC - https://www.cnbc.com/2026/06/12/spacex-ipo-spcx-live-updates.html

[3] Initial Public Offerings: Why Individuals Have Difficulty Getting Shares - SEC / Investor.gov - https://www.investor.gov/introduction-investing/investing-basics/glossary/initial-public-offerings-why-individuals-have

[4] Updated Investor Bulletin: Investing in an IPO - SEC - https://www.sec.gov/resources-for-investors/investor-alerts-bulletins/updated-investor-bulletin-investing-ipo

[5] Understanding the IPO Share Allocation Process - Fidelity - https://www.fidelity.com/learning-center/trading-investing/trading/ipo-share-allocation-process

[6] BitMart IPOPrime - BitMart - https://www.bitmart.com/en-US/ipoprime/space-x