Definition of 'All-Holders Rule'
An SEC regulation that requires a tender offer to be made available to all holders of the identical class of the security. The All-Holders Rule is specified in Rule 14d-10 of the Securities Exchange Act of 1934, which specifies equal treatment of security holders. This rule is especially important during takeover bids, ensuring that any tender offers made by the acquiring company cannot be directed to only those shareholders in favor of the takeover.
Investopedia explains 'All-Holders Rule'
For example, if company ABC has tendered an offer to buy back its B class shares, then all holders of this class must be allowed to participate in the buy back. The SEC does not require ABC to offer this buy back to the shareholders of its other classes.
A corollary to the All-Holders Rule is that the consideration paid to all security holders who tender their securities should be the highest or "best price." This is intended to prevent some security holders receiving a lower price for their securities than others in a tender offer.