First, distinguish between LULD and halt codes.

LULD is a price band and trading halt mechanism for handling rapid price fluctuations. LUDP refers to a trading halt due to volatility in the Nasdaq Trader code table. M is also a volatility halt, and the corresponding code table describes it as a halt for exchange-listed securities with market classification C. Do not confuse it with other codes like M1 or M2.

Upper/lower limit halts are informal terms for situations where prices move rapidly in either direction and then pause. These are not the same as the daily price limits for Korean stocks and must be distinguished from market-wide circuit breakers. You cannot determine the direction of the halt or the future price movement upon resumption based solely on LUDP or M.

The four moving numbers are all different.

First, identify whether the large number on the screen is the last traded price, the bid/ask quote, or the indicative auction price. Other fields may change while the last traded price before the halt remains displayed.

Why do quotes move when trading is halted?

A trading halt does not mean all numbers are frozen. During quote-only periods or auctions preparing for resumption, order entries, modifications, and cancellations permitted by exchange rules can change the information. The indicative auction price also changes based on newly gathered orders. You must verify whether order processing or cancellation is possible based on the exchange's phase and your brokerage's support.

Nasdaq has provided guidance in cases where it displays the reference price for NOII (Net Order Imbalance Indicator) identically on both the buy and sell sides during the quote-only period of a halt. This means that display methods may differ from depth-of-book quote feeds. The fact that both prices are the same does not mean you can immediately buy or sell, nor does it mean normal execution is proceeding.

It may look different depending on the brokerage firm.

Brokerages may differ in the exchange/consolidated market data feeds they receive, the depth of quotes subscribed to, real-time vs. delayed conditions, and update or display methods. For example, IBKR provides guidance on cases where Level I and Level II displays differ based on market data permissions. Do not interpret the order book of a single app as the order book for the entire US market.

However, there is no basis to conclude that a specific domestic brokerage is unconditionally more accurate or that they are showing fake quotes during a halt. Compare the same ticker, time, and field, and verify the data source and display policy during halts with the respective brokerage. A single screenshot cannot confirm the cause of a discrepancy.

A large volume of buy orders does not mean a limit-up reservation.

Suppose the indicative resumption price hypothetically rose from 10 dollars to 11 dollars. If buy orders subsequently decrease or sell orders increase, the indicative price may fall again. Even in continuous trading after the final auction execution, the direction can change based on new orders and news. This example illustrates the principle that the exchange does not guarantee the next price.

Quotes come with conditions and observation points. You cannot simultaneously see orders that will be canceled, orders not visible on the screen, or information from other trading venues. It is risky to judge that a stock will "definitely rise upon resumption" based solely on the remaining order ratio or the color of a quote. You cannot conclude that someone has manipulative intent just because the numbers have changed.

Distinguish between expected price, resumption of quotes, and resumption of trading.

Official sources may provide separate times for quote resumption and trading resumption. Do not assume trading has resumed just because 5 minutes have passed or a service timer has ended. If the conditions for the resumption auction are not met or additional reasons for a halt arise, the wait may continue.

Market orders placed immediately after resumption may be executed at prices significantly different from the price just before the halt or the expected price on the screen. Limit orders set price conditions but do not guarantee execution. You must also distinguish between order submission/cancellation requests and the actual completion of execution/cancellation.

The order to check before quotes.

You can use quotes as observational data. However, the key is not to treat them as definitive signals for future direction.

1. 1

   Check the official halt code, halt time, listing market, and subsequent announcements.

2. 2

   Check whether you are looking at the last traded price, general quotes, or the expected auction price.

3. 3

   Check the data coverage and timing, and do not simply aggregate numbers from different apps.

4. 4

   Verify official trading resumption and actual execution details. Do not assume that you can sell at the expected price.

Check what you have read.

• Have you distinguished between the code and the direction of the rise or fall?
• Have you checked the types of numbers and data visualization?
• Did you compare data from the same range as other brokerage firms?
• Have you confirmed the official status of resumption, execution, or cancellation?

Apply what you read to the actual screen

Try it on WAPE

Recommended for continued reading.