Form 13F: What Must Be Reported

Ever wonder how financial media reports "here's what Warren Buffett bought last quarter"? The answer is Form 13F — a quarterly SEC filing required of any institutional investment manager that exercises investment discretion over at least $100 million in qualifying US equity securities. It lists every position above certain minimums: the security, the number of shares, and the market value, as of the last day of the quarter, filed within 45 days after quarter-end.

This creates a genuinely useful, freely available window into what large institutional investors are holding — hedge funds, mutual funds, pension funds, insurance companies are all in scope. It's why entire websites and data products exist just to aggregate and compare 13F filings across managers, and why "13F season" (the weeks after each quarter-end deadline) draws real attention from journalists and other investors trying to spot trends in what smart money is doing.

But the filing has real limitations that trip up anyone using it uncritically. It only covers long equity positions in scope of the rule — no short positions, no derivatives in most cases, no non-US securities, no cash. A fund that's short a stock through options or has hedged a long position with a swap will show up in a 13F looking simply "long," with the hedge invisible. And because it's a snapshot as of one date filed up to 45 days later, by the time you read it, the position may already be significantly different — a fund could have exited the position entirely the day after quarter-end and you wouldn't know for another quarter.