A 13D is a document filed to disclose the ownership of registered equity services. It has to be filed with the Securities and Exchange Commission (SEC) and with the relevant stock exchange(s) within 10 days of when an individual, a company or a related group buys 5% or more of any class of a public company’s stock. The filing also has to disclose which individual or group holds voting power over the shares.

These filings are available at the SEC website. and through a number of paid services like Edgar Online. In this article, we’ll show you what you can learn by following these filings.

Signals or Signs of Change

The presumed reason behind the existing 13D regulations is that investors who take large positions in stocks can affect their trading patterns and prices. This is especially true for stocks that don’t trade a large daily volume. For example, when FastChannel (DGIT) purchased of 11% of Point.360 (PTSX) in a privately negotiated transaction on Dec. 22, 2006, PTSX’s stock rose by 37% the following day. In other words, for wary investors, a 13D regulation can present an opportunity for stock price appreciation.

The 13D may also be a precursor to a takeover attempt on the part of an outside investor, or part of a process to gain seats on the board or de facto control of the company by owning a large, controlling block. (For related reading, see The Basics Of Mergers And Acquisitions and Trade Takeover Stocks With Merger Arbitrage .)

The filing of 13Ds is the most important signal to investors that a change of control at a company may be underway or that an investor is trying to get management to make changes to increase shareholder value through methods such as cost-cutting or the sale of part or all of the company.

When an investor purchases more than a 5% share in a company and files a 13D, that investor may also attach a letter to management explaining the reason for the action. These letters are usually critical of management and the board directors, and address the reasons that the investor believes the company’s stock is undervalued. In a November 2006 letter to the management of Advocat (AVCA), Bristol Capital Advisors and Oakdale Capital Management requested a stock split to increase trading volume in the company. Bristol and Oakdale stated the purpose of their investments and their desire for significant change:

While we appreciate that Advocat represents what we believe to be the most compelling opportunity in the nursing home sector due to your low occupancy rates and relatively poorer payer mix relative to your peers (factors that we perceive as opportunities, not risks), your low daily trading volume has impeded the ability of sophisticated investors to take advantage of the opportunity and has resulted in Advocat trading at a substantial discount to the valuation of its peers . As you have rejected our offer to acquire the Company, we ask that you do what is in the best interests for all the shareholders and engage immediately in a 3:2 share split as well a share repurchase program .

The implied threat is that if management will not act, the shareholder may take further steps. (For related reading, see Evaluating A Company’s Management .)

Another high profile 13D was filed when corporate raider Carl Icahn bought more than 5% of Time Warner in 2005. He began the process of getting two board seats and even got investment bank Lazard to set a value on each of the company’s units in the event of a breakup. (To learn more, read Use Breakup Value To Find Undervalued Companies .) This gives Icahn the right to use his shares to attempt to unseat management if he is not happy with the company’s results in the future. The effect was a significant rise in the stock’s price.