Why the last after-hours trade is not the NYSE opening price
On the NYSE, the last extended-hours trade, the bid and ask, and the opening-auction price are three different numbers. The auction price is not required to equal the last trade from the night before. This article applies to NYSE-listed securities and the NYSE opening auction. Nasdaq, NYSE Arca and other exchanges run different auctions at different times. Their rules are not described here.
NYSE timeline
Times below are US Eastern Time and come from NYSE’s current auctions page for NYSE-listed securities.
- 6:30 a.m. Order entry opens. Orders can be entered and cancelled until the designated market maker opens that security. The open can be later than 9:30.
- 8:00 a.m. Imbalance information is published every second, when it changes, until the stock opens.
- 9:30 a.m. The opening-auction process begins. That clock time is the start of the process, not a promise that every stock has already printed its auction price.
NYSE’s opening-and-closing fact sheet says only NYSE-listed securities take part in this opening auction, and that the designated market maker opens each security. FINRA’s extended-hours note is broader than the NYSE: an extended-hours trade does not change the official closing price, and it does not set the next day’s opening price. During regular hours, brokers generally must use the consolidated best bid and offer. FINRA says that consolidated quote is not published in the same way outside regular hours, and that venues are not linked in the same way.
Hypothetical example, not a market print. Example Co. is an invented NYSE-listed company. None of the prices below was observed.
- 4:00 p.m. the previous day: official close 50.00. This is a regular-session price.
- 6:10 p.m.: a broker screen shows a last trade at 52.40. That is one completed extended-hours trade. It is not the NYSE opening auction.
- At the same moment the screen shows a bid of 52.10 and an ask of 52.80. Those are quotes. Neither one has to be a trade.
- The next morning the NYSE opening auction prints 51.10. That figure is the auction price in this example. It does not have to equal 52.40, and 9:30 is when the auction process begins, not proof that this invented stock opened at that second.
From these invented numbers you can see the labels. You cannot say the stock opened at 52.40. You also cannot call 51.10 minus 52.40 an auction error. The last trade, the quote and the auction were formed differently.
Before comparing your screen with the NYSE opening price
- Check the field. Is the number a completed last trade, the bid, the ask, an indicative auction price or the official opening print? A quote is not a completed trade.
- Check the session. Distinguish the previous regular-session close, after-hours activity, next-day pre-market activity and the NYSE opening auction.
- Check the timestamp and time zone. A stale last trade or delayed feed can remain on screen while current quotes change.
- Check the venue. An NYSE-listed stock can trade on other venues. The last extended-hours trade displayed by a broker is not automatically an NYSE opening-auction trade.
- Check whether the stock has actually opened. NYSE’s opening process starts at 9:30 a.m. Eastern Time, but an individual security may open later. An indicative price before its opening is not the final auction price.
In the hypothetical example above, 52.40 is a last trade, 52.10 and 52.80 are quotes, and 51.10 is the invented next-day opening-auction price. Different labels explain why they need not match. They do not tell us which way the stock will move next.
For the mechanism and the risks, see NYSE’s auction timelines and FINRA’s extended-hours trading explanation. This checklist concerns the NYSE opening auction; it does not substitute for another venue’s rules.
When this does not apply
- The security is not listed on the NYSE. Another exchange’s open is a different mechanism.
- The figure called the open is the first trade on a different venue, or a broker’s extended-hours last sale.
- 52.40 in a real screen is a bid or an ask rather than a last sale. The example above keeps those labels apart.
- The session is a halt or a holiday. The example assumes an ordinary NYSE session.