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Key Takeaways
- A U.S. equity dark pool matches orders without publishing its resting order book.
- Its operator is a registered broker-dealer, and an NMS stock ATS publicly files Form ATS-N.
- Completed listed-stock executions enter the trade-reporting system and consolidated tape.
- The worked 300,000-share midpoint cross improves the seller’s price by $4,500 relative to the displayed bid.
- Track large executions, compare repeated price levels and connect the activity with options flow.
What is a dark pool?
A dark pool is a trading venue that matches stock orders without publishing a public resting order book. In U.S. equities, its operator is a registered broker-dealer operating an alternative trading system. NMS stock ATSs file public Form ATS-N disclosures about their operations.
Completed executions enter the reporting system and the consolidated tape. Their prices and sizes give traders another view of liquidity alongside the displayed market.
How dark pools work: a midpoint cross example
A fund is working a 500,000-share sale in XYZ, a stock with average daily volume of 4 million shares. The displayed best bid is $48.72 and best ask is $48.75. It seeks a midpoint match without publishing the full remaining order.
- Midpoint = ($48.72 + $48.75) / 2 = $48.735
- Executed slice = 300,000 shares at $48.735, worth $14,620,500
- Price improvement versus the $48.72 bid = $0.015 per share × 300,000 = $4,500
- Executed slice as a share of average daily volume = 300,000 / 4,000,000 = 7.5%
- Shares remaining in this specified parent order = 200,000
The fund completes 300,000 shares at $48.735, improving proceeds by $4,500 relative to the displayed bid. Track that reported execution price alongside subsequent stock trading and options activity.
How traders read dark pool executions
Read each print’s price, size and execution time. Group repeated executions near the same price and compare their size with the stock’s normal and session volume.
Then follow the stock’s response around those prices. Compare retests, holding above or below the area, and expanding volume with options flow in the same name. This connects the equity executions with the options activity and the developing price setup.
Dark-pool flow lists large reported executions and the levels they form, and the options profit calculator compares entry cost and payoff at those levels.
Limitations of dark pool data
- Read a trade report as the completed slice. It shows the price, size and time of a completed trade, while the resting orders and the rest of the parent order, such as the worked fund’s 200,000 unexecuted shares, stay out of view.
- Read the side from the stock’s response. A midpoint print has a buyer and a seller, and the report does not say which side started the trade or why.
- Pools differ in who can trade, which order types they accept and how they match orders. An NMS stock ATS describes these terms in its Form ATS-N, so read that filing for the venue’s rules.
- Read the off-exchange tape as a whole. Off-exchange trade reports cover dark pools and broker-dealers that fill orders internally; together they show where institutional size traded away from the exchanges.
- Confirm a repeated price level with the stock’s response. Retests, holds and expanding volume show the level is working, and price can trade straight through one that is not.
Bottom line
A dark pool lets large orders trade without showing the resting book, and its completed listed-stock trades still reach the consolidated tape. Read those prints for price, size and time against the stock’s normal volume, group repeated levels, and confirm them with the stock’s response and options activity before treating any level as meaningful.
Clear answers
Frequently Asked Questions
Sources and Further Reading
- SEC: Regulation of NMS Stock Alternative Trading Systems
- SEC: Alternative Trading Systems
- FINRA: OTC ATS and Non-ATS Transparency
- FINRA: Can You Swim in a Dark Pool?
How entries are sourced, calculated and updated: editorial methodology.