Usually a corporate action, not a trade. A disclosed portfolio is a list of instruments on one date, and several things move that list without the fund manager doing anything. Compare two months straight out of the raw files and those show up as activity that never happened.
1. The quantity moves and the value does not. A bonus issue or a face value split multiplies the number of shares on its own, with no buying involved. The share count can double while the position is worth exactly what it was worth before. So the two columns have to be read together: a change in quantity and a change in market value mean something only as a pair. Quantity up and value flat is an action by the company. Quantity flat and value up is the price. Both moving together is usually the fund.
2. The same company appears as an exit and as a new entry, on the same day. A face value split gives the company a new ISIN, and the old one stops. Nothing in the file says the two lines are the same business, so a naive month-on-month comparison reports a full exit and a full fresh purchase. The fix is a remap, done each month, matching the retired identifier to its replacement before anything is compared. Until that is done, a change report on raw files overstates both entries and exits.
3. Not everything in the file is a share. There is a tail of short-term debt at the bottom, and it can run to dozens of rows, because a fund holds the same bank's certificate of deposit at several maturity dates and every maturity is a separate instrument with its own ISIN. Left as they come, those rows crowd out the equity. Grouping them is what makes the equity list readable, and it also stops a rollover between two maturities reading as a trade.
What to do with it. Tag entries and exits rather than inferring them from a diff, keep quantity change and market value change as separate columns, remap ISINs before the comparison, and sort by the outliers - the oddities come to the top quickly and most of them turn out to be an action rather than a decision.
Eleven month-end snapshots across 24 of India's larger equity funds, with entries and exits tagged and both change columns side by side: https://www.tigzig.com/mfpro (Composition). The identifier question one level up, at the fund rather than the holding: https://www.tigzig.com/agents-faq/should-i-join-fund-data-on-name-isin-or-scheme-code. Write-up: https://www.tigzig.com/post/mfpro-composition-august-portfolios-sep2026.
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