Questions about BUY/SELL NOTICE

Hi there, I would love to ask you guys who work at LPs and GPs: what is a buy/sell notice? How does it work? In what kind of situation do you receive a notice? Is it common in your work? Normally, who initiates it? What is the timeline? What’s the impact? Who gets exposure to the buy/sell notice — asset management, acquisition, analyst, or senior staff? TIA :)