How IPOs work: from filing to first trade

The S-1 filing: the company on the record

The IPO process starts with paperwork, not marketing. The company files a registration statement, known as the S-1, with the Securities and Exchange Commission. Inside sits the prospectus: a detailed account of the business model, audited financial statements, management backgrounds and compensation, the intended use of the offering proceeds, and a risk-factors section that catalogs everything that could go wrong. The risk-factors section is often the bluntest part of the document and repays a careful read.

The SEC reviews the filing and typically sends back rounds of comments, which the company answers by amending the S-1. Each amendment is public, so anyone can watch the disclosure sharpen over the process. During this period the company operates under quiet-period restrictions that limit what it can say publicly about the business beyond the filed documents, which is why pre-IPO hype should always be checked against the prospectus rather than taken at face value.

For the reader, the S-1 is the primary source that matters most. Every claim in later marketing traces back to it, and the research lesson shows how to verify company statements against filings rather than press coverage. If a fact is not in the prospectus, treat it as unverified.

Underwriters: the banks running the deal

The company hires investment banks as underwriters to manage the offering. Their job spans the whole deal: advising on timing and structure, running due diligence, preparing the marketing materials, assembling a syndicate of banks to distribute the shares, and ultimately buying the shares from the company and reselling them to investors. In the common firm-commitment structure, the underwriters purchase the offering and bear the risk of reselling it, which is why their fees are substantial.

Underwriters also receive an overallotment option, known as the greenshoe, typically covering up to about 15 percent more shares than the base offering. It works as a stabilization tool: the banks can sell the extra shares into strong demand, and if the stock dips after listing, they can buy shares back in the open market to support the price while covering their short position. The greenshoe is one reason first-day trading sometimes looks calmer than the underlying demand would suggest.

Roadshow, book building, and pricing

With the filing in review, management goes on the roadshow: a tour of presentations to institutional investors, laying out the business, the growth story, and the use of proceeds. The prospectus at this stage carries a price range rather than a fixed price. As the roadshow progresses, the underwriters collect indications of interest from institutions, a process called book building, which reveals how much demand exists at various price levels.

The final offer price is set the evening before trading begins, balancing two goals that pull in opposite directions: the company wants to raise as much capital as possible, while the underwriters want enough demand left over for the shares to trade stably on day one. A price set too high risks a broken deal that falls on the open; a price set too low leaves money on the table and produces the famous first-day jump. Allocations at the offer price go overwhelmingly to institutional investors and select brokerage clients, not to the general public.

Two pricing outcomes are worth understanding rather than celebrating or lamenting. An offering priced above its range signals strong roadshow demand; one priced below its range signals the opposite. Neither predicts the company's long-term trajectory. The price is a negotiated starting point for public trading, not a verdict on value.

The first day of trading

On listing day the shares open for trading on the chosen exchange under their ticker symbol. There is no continuous price history, so the opening auction matches buy and sell interest to find the first public price, which can take well into the morning for heavily watched deals. From there the stock trades like any other listed security, except that volatility is usually higher: the market is discovering the price in real time with no chart history to anchor expectations.

The underwriters may stabilize the price in the early days, buying shares under the greenshoe mechanics described above. Stabilization can cushion declines but cannot hold up a price the market rejects; it is a shock absorber, not a floor. Most individual investors first get access at this stage, buying in the open market at whatever price the auction sets. That is a different proposition from buying at the offer price: the first-day jump that makes headlines is a gain for allocation recipients, while open-market buyers pay the post-jump price and inherit the volatility that follows.

Lock-ups: the supply cliff after the debut

Not every share is free to trade on day one. Insiders, employees, and early investors typically sign lock-up agreements barring them from selling for a set period after the IPO, commonly around 180 days. The lock-up exists to prevent a flood of insider selling from overwhelming the new public market in its first months.

When the lock-up expires, a large block of previously restricted shares becomes legally sellable at once. Whether holders actually sell is unknowable in advance, but the mere possibility of new supply can pressure the price into the expiry date, and heavy actual selling can extend the pressure after it. The expiry date is public information disclosed in the prospectus, which is why it belongs on any IPO watchlist. The market events calendar tracks confirmed IPO dates; lock-up expirations derived from those dates deserve the same verification against the prospectus before being treated as fact.

The risks that deserve a sober read

IPOs concentrate several risks that seasoned public companies do not carry, and the prospectus risk-factors section exists precisely to list them.

Limited public track record. The audited financials in the S-1 may cover only a few years, and the business has never operated under public-company scrutiny. Projections in the marketing materials are aspirations, not history.

No price history. There is no trading record to judge valuation against, no analyst coverage history, and no established shareholder base. The market is pricing the company from scratch, which is why early volatility is the norm rather than the exception.

Lock-up overhang. The coming supply from lock-up expirations is a known future event with an unknown market reaction. It is a structural feature of every IPO, not a surprise, and it should be priced into expectations from the start.

Hype and dilution. Heavily marketed deals can open at prices that assume years of flawless execution, and young public companies often return to the market with follow-on offerings that dilute early shareholders. The excitement of listing day and the economics of the years after are two different things.

None of this makes IPOs inherently good or bad investments; it makes them a category where the facts in the prospectus matter more than the narrative around the listing. Read the filing, note the lock-up date, and decide what the business is worth before the market tells you.