Block trade (options)
A block trade in options is a single large execution, frequently negotiated away from the public order book and then reported to the tape under a specific trade condition. Its size is visible; the counterparties, their intent and any linked hedge are not.
Senzoukria · Glossary · Updated September 2026
Definition
The word block describes size, not method. Exchanges define minimum quantities for trades that may be arranged privately between two parties and then printed on the exchange, and those prints carry trade conditions identifying them as negotiated. In everyday flow language, however, any single execution above a tool's size threshold is called a block whether or not it was negotiated. The two meanings should not be mixed: an exchange-defined block has a documented condition code, while a scanner's block is a filter setting.
Blocks are common in hedging and in position rolls, where one party wants a precise quantity at one price rather than sweeping displayed liquidity.
Block versus sweep
| Block | Sweep | |
|---|---|---|
| Shape on the tape | One print | Many prints in milliseconds |
| Where it executes | Often negotiated, printed on one venue | Across venues or price levels |
| What it suggests | A precise quantity at one price | Urgency to fill now |
| Detection | Size threshold or trade condition | Grouping rule with a time window |
What size does not tell you
- A large put block can be portfolio protection, a closing trade, or half of a collar; the other half may have printed on a different underlying.
- The execution price of a negotiated block may sit between bid and ask, which makes side classification ambiguous.
- A block's premium is the dollars exchanged on that print, not the risk the buyer carries; delta and the rest of the position are unknown.
- Block frequency depends on the underlying: ETFs and indices with deep liquidity see negotiated prints routinely.
In Senzoukria
The Option Flow module does not carry a dedicated block tag. Large single prints are found through the Size filter (thresholds of 10, 50 and 250 contracts) and the Premium filter ($10K to $500K), and the header's Biggest trade statistic reports the largest single print of the session. Each print keeps its Side, Price and Vol/OI columns, so a block can be examined against the quote and, through Vol/OI, its own size can be compared with the contract's standing open interest; when the open interest is not available the table says "Open interest unknown for this contract" instead of showing a ratio. Trade condition codes depend on what the configured options source transmits.
Common mistakes
- Calling every print above a size filter a negotiated block.
- Assigning a direction to a block that printed mid-quote.
- Reading a large put block as a bearish bet without looking for a matching stock or futures hedge.
- Comparing block sizes across underlyings with different contract multipliers.
Related
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Frequently asked questions
- Are block trades bullish or bearish?
- Neither on their own. A block reveals that a large quantity changed hands at one price. Whether the buyer or seller initiated, whether the position is new or closed, and what else was traded against it are not on the print. Any directional reading has to be tested as a rule over many cases.
- How can I tell a negotiated block from a large screen print?
- Through the trade condition reported with the execution, when the feed carries it. Exchanges flag negotiated and cross trades with specific codes. Without that field, a large single print is just a large single print, and a size filter should be described as such.
- Do blocks move the underlying?
- A negotiated block is arranged away from the displayed book, so its execution does not consume visible liquidity in the option. Any effect on the underlying would come from hedging, which is not identifiable from the print and may be spread across instruments and time.