What a 13F filing tells you, and what it doesn't

Managers with at least $100 million in US-listed stocks and certain other securities must file within 45 days after each quarter ends. So holdings as of June 30 can appear as late as mid-August. By then the fund may have sold.

• Each long position in US-listed stocks and ETFs: number of shares and value at quarter end.
• Listed call and put options, by the number of shares they cover.
• Comparing two filings shows what was bought, added to, reduced or sold.

• Short positions. A fund can look bullish on paper while betting against the same sector.
• Bonds, cash, most foreign stocks and private investments.
• When during the quarter something was bought, and at what price.
• Why. A position may be a hedge, part of a pair trade, or held for a client.

Treat a 13F as a list of ideas, not a set of trades to copy. A new position from a concentrated, long-term fund says more than a small change at a fund holding thousands of stocks. If an idea interests you, write down your own reasoning and what would make you wrong before acting on it.

SoFo's public filings pages show the latest holdings and changes for funds such as Berkshire Hathaway, Pershing Square and Scion, measured from the day each filing became public. US House members file their trades separately, under the STOCK Act, within 45 days and as ranges of amounts; see Nancy Pelosi's trades.