Although cocoa powder does actually expire, it is typically labeled with a "best-by" date. This indicates quality, rather than safety. When properly stored, cocoa powder can last for at least two years after the printed date if unopened or one year once opened.
Beyond this time, the flavor and quality of the cocoa powder dissipates. Powdered hot chocolate or cocoa mixes, on the other hand, often do expire. Because these typically contain powdered milk, they should be used within six to 12 months of purchase. Cocoa powder should be stored in a cool, dry location to extend its shelf life. If the powder no longer has a chocolate taste, it should be discarded.