A block trade is a privately negotiated options transaction of at least 50 contracts (varies by exchange) that is executed off the public order book and then reported to the exchange. Blocks allow institutions to move large size without impacting the displayed market.
⚡ KEY TAKEAWAY: Block trades at or near the ask price suggest aggressive buying. If you see a 5,000-lot block bought at the ask on puts your short strike aligns with, consider adjusting your position before the flow hits the screen.
Why It Matters
Block trades reveal institutional positioning that does not appear on the public order book until after execution. For premium sellers, blocks at or near your short strikes from institutional participants carry more significance than equivalent retail flow.
How It Works
Block trades are privately negotiated between institutional counterparties, then reported to the exchange tape after execution. Minimum size requirements vary by exchange (typically 50+ contracts). Blocks trade at or between the NBBO and are flagged on time-and-sales feeds with a block condition code.
Example
A 5,000-contract block of AAPL 180 puts trades at $4.20, slightly above the $4.15 ask. This is aggressive buying at a premium to the public market, suggesting urgency. A premium seller who is short the 175 puts should consider tightening their stop or rolling down, as the institutional buyer expects AAPL below 180.
Common Mistakes
Traders assume all blocks are directional bets. Many blocks are delta-neutral hedges, portfolio rebalancing, or structured product flows. A block put buy by an insurance company hedging a structured note is not bearish flow. Check whether the block was accompanied by stock or other option legs.
A block trade is a privately negotiated options transaction of at least 50 contracts (varies by exchange) that is executed off the public order book and then reported to the exchange. Blocks allow institutions to move large size without impacting the displayed market.
Why does Block Trade matter for premium sellers?
Block trades at or near the ask price suggest aggressive buying. If you see a 5,000-lot block bought at the ask on puts your short strike aligns with, consider adjusting your position before the flow hits the screen.
How does Block Trade work?
Block trades are privately negotiated between institutional counterparties, then reported to the exchange tape after execution. Minimum size requirements vary by exchange (typically 50+ contracts). Blocks trade at or between the NBBO and are flagged on time-and-sales feeds with a block condition code.
What are common mistakes with Block Trade?
Traders assume all blocks are directional bets. Many blocks are delta-neutral hedges, portfolio rebalancing, or structured product flows. A block put buy by an insurance company hedging a structured note is not bearish flow. Check whether the block was accompanied by stock or other option legs.
