if news pending and no particular news if stock it will drop immediately a big number, never buy if you hear this situation and all existing position will be a loss, example UUU went up 13.8 and news pending, after company said no news, when open again it dropped under 7
T1 halt - release news (more common)
T12 halt - require additional information needed (stock exchange requests)
LUAD halt - change 10% in 5 min, or 10 min
NYSE halts
https://www.nyse.com/trade-halt-current
NASD halts
https://www.nasdaqtrader.com/trader.aspx?id=TradeHalts
Halt codes
http://www.nasdaqtrader.com/Trader.aspx?id=TradeHaltCodes





