Form 13F
The quarterly SEC filing that discloses the US equity holdings of large institutional investment managers.
A Form 13F is a quarterly report that institutional investment managers with at least 100 million dollars in qualifying US equity assets file with the SEC. It lists long positions in exchange-traded stocks, certain options and ETFs as of the quarter end. It is due within 45 days of quarter end.
On our site, 13F holdings are shown by manager and quarter, with changes in share count. The filing is a snapshot at quarter end and does not show trades made after that date.
Traders care because the filings show which funds added or cut positions, and they are read as a signal of institutional conviction. The delay of up to 45 days makes them a lagging indicator.
Worked example (illustrative numbers, not real data): a fund's 13F shows 2 million shares of a company at the end of June and 3.5 million at the end of September. The 1.5 million share increase is visible, but the trades happened over the quarter, and the stock may have moved since.