Both block deals and bulk deals show up in NSE's data as unusually large trades. It is tempting to treat them as the same thing - "someone big bought (or sold) a lot of this stock." They are fundamenally different and mixing them up means missing what each one is saying.
Block deal: one negotiated trade
A block deal is a single, privately negotiated transaction between two parties, above a minimum size set by exchange rules. A block deal is executed through a separate trading window outside the normal market, typically before the regular session opens. Two counterparties agree on a price directly and report it to the exchange. One block deal is one line in the day's report - one buyer, one seller, one price, one quantity.
Because it is negotiated directly rather than through the order book, the price is often close to the prevailing market price. This deal is less about moving the market and more about transferring a large position efficiently, without the price impact.
Bulk deal: one client's whole day, aggregated
A bulk deal is different in kind, not just in size. It gets reported when a single client's total buying or selling of one stock in a single day through the ordinary market, potentially across many smaller trades crosses a threshold. This threshold is a fixed percentage of the company's total shares. There is no separate window and no single counterparty to point to. It is an end-of-day aggregate of one client's footprint in the regular market.
That means a bulk deal can represent one client quietly accumulating (or exiting) a position across dozens of smaller trades that, individually, would not have stood out at all.
Why the distinction matters
- What it tells you about intent. A block deal is usually a one-off transfer. A fund rebalancing - an existing large share holder exiting to another large share holder. A bulk deal reflects sustained same-day activity by one party, which can be a stronger signal of an actual view being expressed through the regular market.
- Is it likely to recur. Because a bulk deal is behavioral (with a client kept buying/selling all day), it is more meaningful when it shows up for the same client and symbol across multiple days. Persistence of this nature is a much stronger signal than a single day's number. A block deal, by contrast, is usually a discrete event where repetition matters less.
- How we use both together. On this site, Block Deals and Bulk Deals are tracked separately by design but the Smart Money view deliberately merges both over a trailing window. The underlying question - where is unusually large trading activity concentrated right now - is the same either way, even though the shape of that activity differs.
In short, a block deal tells you a big position changed hands once. A bulk deal tells you what one player was doing, in aggregate, all day. Both are worth watching, just not for the same reason.