I'm off to vote but I've literally seen three different explanations all from AI here's one.
From AI
No, companies are not required to tell shareholders ahead of time about every open-market stock buyback, but they must disclose the activity in their quarterly and annual reports. Shareholders are typically informed through a pre-announced authorization, which states the maximum amount the company is authorized to repurchase, but this is just an intention, and there is no guarantee when or if any shares will be bought.
Market Data 
Markets 
AI
