A block deal is a single, very large trade executed between two parties in a separate exchange window, at a pre-agreed price, away from the regular order book. A bulk deal is not a special trade type at all. It is a label the exchange applies when someone's ordinary-market buying or selling in a stock crosses a size threshold in a day, triggering public disclosure.
Why do big investors need a separate window?
Size. If a fund wants to sell shares worth hundreds of crores, dumping that into the normal order book would crush the price long before the order finished filling. The visible supply would scare buyers away (the same problem disclosed quantity tackles at retail scale, but far bigger).
So the exchanges run a block deal window: short, designated sessions during the trading day where two institutions that have already agreed on a quantity and price can cross the trade in one shot. Key features:
- Minimum size. Only trades above an exchange-set value threshold (running into crores) qualify. This is strictly a big-ticket facility.
- Price band. The agreed price must sit within a small percentage band around the prevailing market price, so the window can't be used to trade at fantasy prices.
- All-or-nothing. The order must match in full within the window; it doesn't rest in any book.
- Disclosure. Executed block deals are published by the exchange, naming the parties, quantity, and price.
Because the trade never touches the regular book, your open orders and the live price aren't directly swept by it, though the market often reacts to the news of who bought or sold.
What makes a deal a "bulk deal"?
A bulk deal happens in the normal market, through the same matching engine as your own orders. The exchange simply tags it after the fact: if a single client's total buying or selling in a stock during the day crosses a threshold percentage of the company's shares, the broker must report it, and the exchange publishes the client's name, quantity, and average price.
| Block deal | Bulk deal | |
|---|---|---|
| Where it trades | Separate exchange window | Regular order book |
| Price | Pre-agreed, within a band | Whatever the market gives |
| Counterparty | Known in advance | Anonymous, like any trade |
| What defines it | Minimum trade value | Day's volume crossing a % of shares |
| Impact on live price | None directly | Full market impact |
Why should a retail investor care?
You can't participate in either, but both are public information. Exchanges publish daily block and bulk deal lists, and many investors watch them to see what large institutions and well-known investors are doing in a stock. Treat that as context, not a signal: a fund may sell for reasons (redemptions, rebalancing) that say nothing about the company. Large flows also interact with a stock's liquidity. A bulk sell in a thin counter can move the price sharply during the day.
Things to keep in mind
- Block deals happen off the regular book at a pre-agreed price; bulk deals are ordinary trading that crossed a disclosure threshold.
- The exact thresholds, minimum block value, the block window timings, the price band, and the bulk-deal percentage, are set by the exchanges and revised periodically; check current values before relying on them.
- Disclosure is after the fact; by the time you read a deal list, the price may already reflect it.
- A big name buying or selling is context about flows, not a recommendation to copy the trade.
Read next
What are order freeze limits in F&O? — The ceiling that stops a single order from destabilising the book.