Hindsight Markets / Glossary

How to trade halts and resumptions

Updated 23 October 2026 · By Hindsight Markets

When a stock halts, nothing trades until the exchange reopens it with an auction, so you cannot get in or out during the halt and the first price after it can be far from the last one. Trading halts well means planning before the pause: know where the LULD band sits, decide what you will do at the reopen, and size for a gap either way. It is a skill best practised on real halts, because the reopen is where the surprises are.

The kinds of halt

• LULD pause. Automatic, set off by price. A stock that sits at the edge of its limit up-limit down band for 15 seconds pauses for five minutes. On Nasdaq's halt list it carries the code LUDP.
• News or regulatory halt. Called by the listing exchange, often while news is pending, and lasting until the exchange reopens the stock. See news halt and the halt codes.
• Market-wide circuit breaker. The whole market stops after a large fall in the S&P 500. See market-wide circuit breaker.

What happens during a LULD pause

Trading stops for five minutes. Nothing prints on the tape, market orders do not fill, and orders wait for the reopening auction, which sets the first price after the pause. If the auction cannot open within its limits, the pause is extended. The bands run only in the regular session, 9:30 a.m. to 4:00 p.m. ET.

The band's width comes from the previous close and the rules in force on that date. Under the LULD plan's Amendment 18, in force since 24 February 2020, a stock that closed at 3 dollars or less has its band doubled from 3:35 p.m. to the close. The LULD band calculator works out the bands for a price, a tier, a date and a time.

One day, nine pauses: POM on 21 October 2026

POM closed the day before at 1.99, so its band was 20% that day. It paused nine times under LULD, seven of them between 9:35 and 10:25 a.m. An earlier halt, from 3:04 a.m. to 9:00 a.m., carried no reason in the exchange's feed.

Seven of the nine reopened above the last trade and two below, so a pause is no promise of a pop. Two ran past five minutes: the 9:41 pause lasted 10 minutes 7 seconds, and the 3:30 pause did not reopen until 4:00 p.m. The halts, with a clip of each reopen, are on the POM runner page.

The reopen fill

The book is often thin in the seconds after a reopen. Our recap works out what a 5,000-share buy would have cost a second after each of POM's reopens, from that day's full order book:

Where the screen showed fewer shares than the order wanted, the order paid up through the book. That cost is part of the trade, and it is why the size you choose matters most at a reopen. See slippage.

A plan for the reopen

1. Before the pause. Know where the band sits and how far the stock can run before it pauses. A buy at the upper band is the highest price the market allows before the pause.
2. During it. Watch the auction. While the exchange runs it, Level 2 can show the price the stock would reopen at and how much is left unmatched, whenever the exchange publishes it.
3. At the reopen. Decide in advance what you will do if it opens higher, lower or flat, and how much you will pay. A stop cannot fill during the pause, and the stock can reopen past it.
4. The size. Size for the gap, not for the last price. The position size calculator does the arithmetic from your risk and your stop.

Halts in Hindsight Markets

The pauses and halts in a replay are the ones that really happened that day, from the exchanges' own halt messages, and the bands follow the rules in force on that date. During a halt the tape stops while the book keeps updating, market orders do not fill, and a limit order waits for the reopen. The Level 2 and tape reading page shows what the screen looks like in a pause.