After the IPO, shares traded freely in the open market are known as the free float. Stock exchanges stipulate a minimum free float both in absolute terms (the total value as determined by the share price multiplied by the number of shares sold to the public) and as a proportion of the total share capital (i.e., the number of shares sold to the public divided by the total shares outstanding). Although IPO offers many benefits, there are also significant costs involved, chiefly those associated with the process such as banking and legal fees, and the ongoing requirement to disclose important and sometimes sensitive information.
Details of the proposed offering are disclosed to potential purchasers in the form of a lengthy document known as a prospectus. Most companies undertake an IPO with the assistance of an investment banking firm acting in the capacity of an underwriter. Underwriters provide several services, including help with correctly assessing the value of shares (share price) and establishing a public market for shares (initial sale). Alternative methods such as the Dutch auction have also been explored and applied for several IPOs.
The earliest form of a company which issued public shares was the case of the publicani during the Roman Republic. Like modern joint-stock companies, the publicani were legal bodies independent of their members whose ownership was divided into shares, or partes. There is evidence that these shares were sold to public investors and traded in a type of over-the-counter market in the Forum, near the Temple of Castor and Pollux. The shares fluctuated in value, encouraging the activity of speculators, or quaestors. Mere evidence remains of the prices for which partes were sold, the nature of initial public offerings, or a description of stock market behavior. Publicani lost favor with the fall of the Republic and the rise of the Empire.
In the early modern period, the Dutch were financial innovators who helped lay the foundations of modern financial system. The first modern IPO occurred in March 1602 when the Dutch East India Company offered shares of the company to the public in order to raise capital. The Dutch East India Company (VOC) became the first company in history to issue bonds and shares of stock to the general public. In other words, the VOC was officially the first publicly traded company, because it was the first company to be ever actually listed on an official stock exchange. While the Italian city-states produced the first transferable government bonds, they did not develop the other ingredient necessary to produce a fully fledged capital market: corporate shareholders. As Edward Stringham (2015) notes, "companies with transferable shares date back to classical Rome, but these were usually not enduring endeavors and no considerable secondary market existed (Neal, 1997, p. 61)."
In the United States, the first IPO was the public offering of Bank of North America around 1783.