The point
A block deal is a single large trade in one listed stock. Two parties agree the price and the size in advance. That trade runs through a separate window the stock exchanges open outside the regular market. The Securities and Exchange Board of India sets the window's timing, its price band and its minimum size. It reports the trade publicly the same day. The regular market reprices the stock once the window closes.
The two windows a block deal runs in
A block deal never happens inside the normal trading session. It happens in one of two short windows the exchange opens for it, and nowhere else.
The morning window runs from 8:45 am to 9:00 am. It is priced against the previous trading day's closing price. The afternoon window runs from 2:05 pm to 2:20 pm. It is priced against the volume weighted average price of trades between 1:45 pm and 2:00 pm. The exchange works that number out and publishes it in the five minutes before the window opens. Both windows come from a SEBI circular issued on 9 October 2025. The circular overhauled the mechanism and took effect 60 days later.
Outside those two sessions, a total of thirty minutes a day, no block deal exists. A trade placed at any other hour is a regular market order, priced however the order book prices it.
The price band and the minimum size
A single order in the block window has to clear two tests. Its price must sit within 3 percent of that session's reference price. That is a wider band than the 1 percent the exchanges allowed before the 2025 overhaul. Its value must be at least ₹25 crore, more than double the earlier ₹10 crore floor.
Take a stock that closed the previous day at ₹1,000. Its morning block window that day can only print between ₹970 and ₹1,030. That is 6 percent of daylight either side of the reference price. Anything priced outside that band cannot use the window. Anything sized below ₹25 crore cannot either. Both trade in the regular market instead.
A trade that clears the window carries one more condition. It settles as an actual transfer of shares between the two parties. Neither side can square it off or reverse it afterward. A same-day trade in the regular market sometimes can.
Who uses the window, and why
The two sides of a block deal are almost always institutional. A mutual fund, an insurer, a foreign portfolio investor, a private equity fund exiting after its lock-in, or a promoter raising money against part of a stake. An order small enough for the regular order book has no reason to use a window built for size.
The reason is size. Selling several hundred crore rupees of one stock through the regular order book means walking the price down with every incremental order. The buyers waiting at each price level are rarely large enough to absorb the whole position at once. A block deal solves that. Both sides agree the entire size and the entire price before either order reaches the exchange. The trade prints in one line, inside a window built for exactly that.
Why the screen price still moves once the window closes
Mastercard Asia Pacific's exit from Pine Labs, on 22 September 2026, shows the mechanism in one print. Mastercard offered its entire 4.3 percent stake, about 4.97 crore shares, at a floor of ₹179.50 a share. That floor was a discount to the stock's previous close, set to make a block that size easy to fill inside one window. Demand came in stronger than the floor. The shares changed hands at ₹187.75 apiece, for about ₹892.5 crore, and Pine Labs stock rose roughly 6 percent the same day.
A seller pays that discount for certainty inside a fifteen-minute window. The block trade itself had already happened and settled at ₹187.75 by the time the window closed. What moved afterward was the regular market. It repriced the same information every other trader could now see. That included how much stock one large holder had just handed over, and how much demand turned up to absorb it above the discounted floor. That repricing runs through the ordinary order book, on the same stock, once the block window closes and the regular session resumes.
Block deal against bulk deal
A block deal and a bulk deal solve different problems. Headlines often use the two words as if they meant the same thing.
A block deal is defined by the window. It is a trade struck in one of the two sessions above, at a pre-agreed price and size, disclosed by the exchange after market hours the same day. A bulk deal is defined by size relative to the company. Any single trade during the regular session that adds up to more than 0.5 percent of a company's total listed shares counts as a bulk deal. That holds whether it happens in one print or across several trades through the day. The exchange discloses it within an hour of the close.
A single sale can clear both tests at once. That happens when the rupee size is large enough for the block window, and the stake is large enough to cross the bulk threshold as well. Each label is a disclosure category. Neither says anything about direction.
What a block deal print does not tell you
A block deal print records one trade struck on one day. It carries no promise about the next one.
When a deal is oversubscribed the way Mastercard's was, the gap between the floor and the executed price says one thing. Enough buyers wanted that block at that price on that day. That gap is not a promise about where the stock trades a week later. Other holders in the same stock are not bound by it either.
A block deal headline is one data point about a company. It is worth reading. Nothing here is a signal to act on by itself.
What this has to do with a monthly contribution
None of the window, the price band or the ₹25 crore threshold has anything to do with a monthly contribution into a crypto index. A block deal moves one large stake in one listed company. A diversified basket rebalanced on a schedule is a different mechanism entirely.
A stake exit needs a private window because the regular market cannot absorb that much size quietly in one sitting. An index that is designed and rebalanced monthly on a published methodology, the way Qatobit's QSI indices are, runs on a schedule fixed in advance. Every holder sees the same schedule the same way. There is no single seller's exit to manage, and so no separate window to build for one.
For the queue ahead of a company's shares, see what an offer for sale means for the person buying the IPO. What the pre-open market does, and why crypto has none covers the window on the other side of the open. What "the same day" means for a market with no closing bell is in crypto market timings in India and why there is no closing bell. The regular order book a block deal steps around is explained in full at what an order book is. The construction a crypto index rebalances instead of a single stake is covered in what a crypto index is and how it works.
A block deal is a window, a band and a minimum size. It lets one large trade happen without walking the price through the regular book. The screen price that moves afterward belongs to the market, not the deal. The market is catching up on what it just learned.
Frequently asked questions
What is a block deal in the stock market?
A block deal is a single large trade in one listed stock, agreed in advance between two parties. It executes through a separate exchange window instead of the regular order book. Both windows run for fifteen minutes each, under a price band and a minimum value SEBI sets.
What is the difference between a block deal and a bulk deal?
A block deal is defined by when and how it trades: inside one of two dedicated windows, at a pre-agreed price of at least ₹25 crore. A bulk deal is defined by size relative to the company: any single trade exceeding 0.5 percent of its listed shares, wherever it happens during the regular session.
What is the block deal window timing?
The morning window runs from 8:45 am to 9:00 am, priced against the previous close. The afternoon window runs from 2:05 pm to 2:20 pm, priced against the volume weighted average price of trades between 1:45 pm and 2:00 pm.
Does a block deal affect the share price?
A block deal itself settles at its own agreed price inside the window and does not touch the regular order book directly. The regular market can still move once the window closes, as it reprices the information the deal revealed, a separate step from the block trade itself.
Where can I see block deal data?
Both NSE and BSE publish the day's block deals after market hours on their own websites. Each listing carries the stock, the quantity and the price, alongside the same day's bulk deal disclosures.
Crypto investments are subject to market risk. Not financial advice.
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