What is it:
Material nonpublic information is information about a company that hasn't been made public and that a reasonable investor would consider important to a decision to buy, sell, or hold that company's stock. Possessing MNPI prohibits you from trading in that stock, regardless of whether a formal blackout period is in effect.
Why does it matter:
As a senior executive, you're more likely than most employees to come into possession of MNPI in the ordinary course of your job, a pending acquisition, an unreleased earnings result, a material contract win or loss. Understanding this means recognizing that your ability to trade can be restricted at moments your company's blackout calendar wouldn't otherwise flag, since the restriction exists independent of any calendar.
What do people most often get wrong:
People often treat the blackout calendar as the complete picture of when they can and can't trade. It isn't. Possessing MNPI blocks trading at any time, blackout window or not, and the obligation not to trade rests on you personally, not on whether your company's compliance team has flagged that specific date. Many executives manage this obligation by setting up a Rule 10b5-1 trading plan while they hold no MNPI, letting pre-scheduled trades execute automatically rather than relying on their own in-the-moment judgment call.