While not a legal requirement, having employees sign non-disclosure agreements and conflict of interest statements helps to protect your trade secrets and proprietary company information.
This includes changes to its members, changes to share structure, changes to directors and secretaries, and if there is a change to the ultimate holding company of a proprietary company.
The criteria for a large proprietary company are any two of the following: 50 or more employees, assets of $12.5 million or more and revenues of $25 million or more.