When a company lists, not everyone who owns it is free to sell. Regulation and the offer document lock certain holders in for a fixed period, and those periods end on dates you can know in advance.
The ones that usually matter:
- Anchor investors, the institutions that commit a day before the issue opens: a portion is locked for 30 days after allotment, and the rest for 90 days.
- Promoters: a substantial part of their holding is locked for far longer, typically counted in years rather than months.
- Other pre-IPO shareholders: commonly six months from listing, subject to what the offer document says.
Nothing dramatic is guaranteed to happen on an expiry date. What changes is supply. Shares that legally could not reach the market now can, and if the holders sitting on that block choose to sell, more stock meets the same demand. Whether that moves the price depends on how large the block is relative to normal traded volume, and on whether those holders actually want out.
That last point is the one people skip. An expiry is permission to sell, not a decision to sell. Plenty of lock-ins end and nothing observable happens, because the holders stay put.
The reason to know the date is simply that it removes a surprise. If a stock moves sharply and you can see that a 90-day anchor lock-in ended that week, you have a plausible explanation rooted in supply rather than in a story someone invented afterwards.
Where the dates come from: the offer document lists the lock-in categories, their durations and the share counts. We extract them per issue and show them on the one-pager, each figure cited to the page it came from, so you can check us against the source.
None of this is a signal to act on. It is a calendar item, and a reminder that a share price reflects supply as well as sentiment.