The social media company isn't ready to accept Musk's offer to buy it and take it private.
The Friday announcement from the company revealed that it was adopting a poison pill defense.
The shareholder rights plan is a tactic used to avoid hostile takeovers by allowing other shareholders to buy more shares at a discount.
It would make it more expensive than Musk is proposing.
Musk is believed to be the richest person on the planet with an estimated net worth of $259 billion. Musk said in an interview on Thursday that he could afford to buy the company for the amount he proposed.
This course of action is intended to enable all shareholders to realize the full value of their investment, and it will reduce the likelihood that any entity, person or group gains control of the company, according to the announcement.
The plan is due to end on April 14, 2023.
Musk made a $43 billion offer to buy the company. CNBC reported that the board held a meeting on Thursday to discuss the offer.
In a message to the board chair, Musk said he was not playing the back-and-forth game and that it was his best and final offer.
This is not a threat, and it is simply not a good investment without the changes that need to be made.
But during a Q&A session at TED 2022, Musk said he has a Plan B if his offer isn't accepted.
There is a developing story. You can check back for updates.
Ben Gilbert, senior correspondent for Insider, can be reached via email at bgilbert@insider.com. Sources can be kept anonymous. You can use a non-work device to reach out. Please only email PR pitches.