When is a stock delisted?

Delisting means a security loses its eligibility to be traded on the exchange; it may occur at the company's own request or by decision of the exchange on its own authority.

Typical grounds include revenue or market capitalization falling short of requirements, complete capital impairment, an adverse audit opinion or a disclaimer of opinion, insufficient trading volume, final default, and embezzlement or breach of trust. The specific requirements follow each market's listing regulations and have recently been tightening, so check the exchange's rules.