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How Nasdaq Defines Its Official Daily Closing Price

Article Quant Q&A · Author: moshevi
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Summary

The document clarifies why Nasdaq intraday data can contain trades after the regular session ends while a daily close still represents a distinct official value. It explains that the Nasdaq Official Close Price is published at 4:01:30 p.m. Eastern Time, rather than being simply the minute price at 4:00 p.m. or the after-hours price at 8:00 p.m.

The official value may be amended through 5:15 p.m. Eastern Time if trades used in its calculation are canceled or corrected. This distinction matters when matching daily close fields to intraday records or building historical trading datasets. The note provides the definition and timing, but does not explain the detailed calculation methodology or whether every vendor’s unadjusted daily close field uses this specific Nasdaq value; those details may require checking the data source.

Key ideas

  • Nasdaq's official close is a separately published value, not necessarily the 4:00 p.m. minute price.
  • After-hours trading prices do not define the Nasdaq Official Close Price.
  • Nasdaq may revise the official close later if contributing trades are canceled or corrected.
  • Historical data users should verify how their vendor maps the official close into daily price fields.

Tags

EquitiesUS marketsMarket microstructure
Full text
# Time of Nasdaq daily close price


# Time of Nasdaq daily close price












On the Nasdaq website It Is stated that the market closes at 4:00pm.

However I have historic intraday minute prices and I can see that that are minutes with prices after 4:00 PM (I am assuming its After-Hours Trading). I also have historic daily prices.

My question is about the close price (not adjusted close) of the daily data. Is it simply the close price of the minute at 4:00 PM? or Is it the price at 8:00 PM?

## Answer by amdopt (score 3, accepted)

https://quant.stackexchange.com/a/50375

Neither. Nasdaq publishes a close price at 4:01:30 p.m. ET known as the Nasdaq Official Close Price ("NOCP"). Nasdaq also amends this price up to 5:15 p.m. ET if any trades that were used to calculate the NOCP are canceled or corrected.

You can get NOCP prices directly from Nasdaq each day on their website.

Information Links:

NOCP PDF

Nasdaq Press Release

Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.