Why Post-Close Stock Trades Rarely Match the Official Close

Summary

The document compares executing a stock trade after the regular session at the official closing price with submitting a market-on-close order. Its central point is that liquidity typically falls after the close, widening spreads and making execution more costly. A participant willing to trade at the old closing price may be difficult to find once prices and market conditions have moved.

It notes that NYSE Arca may offer trading after the NYSE close and before the open, but those trades occur at prevailing prices rather than the prior official close. The discussion is qualitative and provides no spread measurements, venue rules in detail, or direct comparison of fees and execution costs. Whether an exact-close trade is possible depends on the platform and a counterparty willing to accept that price.

Key ideas

• After-hours liquidity is lower, which can widen spreads and increase trading costs.
• The official close is a past price, and finding a counterparty willing to trade at it later may be difficult.
• NYSE Arca trading outside regular hours uses then-current prices rather than the prior closing price.
• The discussion does not quantify costs or establish whether a specific platform supports execution at the official close.

Tags

# Trading after the close


# Trading after the close












Are there institutions that will fill stock trades after the close (from stock on their order book) at the official close price? If so, would it be significantly more expensive to execute a trade this way than to send a market-on-close order to the same institution?

## Answer by Hunaphu (score 1)

https://quant.stackexchange.com/a/50480

A lot of the liquidity disappears after close, so for that reason alone it is more expensive. The spread is much wider.

To find someone willing to trade on the close price after close is the same thing as trying to find someone willing to trade on the price from 1 pm at 2 pm.

## Answer by Dimitri Vulis (score 0)

https://quant.stackexchange.com/a/54499

After NYSE close and also before open, you may be able to trade on NYSE Arca, but not at any closing price. As the news come in and markets move, the prices move on Arca. (If the price after 4pm moves in your favor, but you still insist on executing at the 4pm close, you should be able to find someone, but I don't think this platform would let you.)

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.