What is a trading halt?
Under certain market conditions, stock exchanges are required by law to halt trading for certain periods of time. During a trading halt, you may not be able to buy or sell stocks and attempted trades orders may be rejected.
Revolut doesn't control market-wide trading halts, which are required by US federal law and implemented by the stock exchanges or a regulatory body. Trading halts can automatically occur when certain market conditions are met, such as significant stock index or price declines.
For more information about this and other trade halts, you can visit this Nasdaq link: Trade Halts – Current.