A large seller who works an order through the normal market moves the price against themselves. The block deal window exists so that a buyer and a seller who have already agreed on size and price can execute in one transaction without either side being pushed around by the order book.
SEBI revised the framework in circular SEBI/HO/MRD/POD-III/CIR/P/2025/134 dated 8 October 2025, Review of Block Deal Framework, applicable from the sixtieth day after issuance. The revised parameters replaced paragraph 1.2 of Chapter 1 of the SEBI Master Circular, which had set a minimum order size of ₹10 crore and a 1 percent price range.
The two windows
| Window | Timing | Reference price |
|---|---|---|
| Morning | 08:45 to 09:00 | Previous day’s closing price of the stock |
| Afternoon | 14:05 to 14:20 | VWAP of cash-segment trades in the stock between 13:45 and 14:00 |
Between 14:00 and 14:05 the exchanges compute and disseminate the VWAP that will apply in the afternoon window.
Current conditions
| Condition | Requirement |
|---|---|
| Price range | Orders within 3 percent of the applicable reference price, subject to surveillance measures and applicable price bands |
| Minimum order size | ₹25 crore |
| Settlement | Every trade must result in delivery; it cannot be squared off or reversed |
| Disclosure | Scrip, client name, quantity and traded price published to the public the same day, after market hours |
The same provisions apply to the block deal window under the optional T+0 settlement cycle.
Caveats
The printed price is constrained by construction. It sits inside a band around a reference the exchange defined, so it is not an independent valuation of the company, and reading a block trade price as a fair-value signal misreads the mechanism.
Mandatory delivery does not mean long-term intent. The buyer must take delivery, and can sell in the normal market the next session.
You learn the transaction, not the reason. Block deals carry promoter stake sales, private equity exits, index fund rebalances and strategic acquisitions with identical disclosure fields, and none of those imply the same thing about the stock.
The parameters have moved recently. Any backtest reading historical block deal data spans periods with a ₹10 crore minimum and a 1 percent band as well as the current ₹25 crore and 3 percent, so the population of trades that qualified is not constant over your sample.