Multiple ownership - multiple plan types

[Guest LSULLIVAN]

Company A was part of a controlled group with Company B. Company A ee's were part of Company B's 401k plan.

Company A was purchased by Company C mid year. Comapny C currently holds a Simple IRA Plan. The total number of ee's from Co C and the acquired number of ee's from Co A will not exceed 100.

Since Co A no longer exists and are now ee's of Co C, doesnt Co A need to stop contributing to Co B's 401k plan? Zero common ownership between Co B and C.

Does Co C need to or required to immediately offer the Co C Simple plan to the former ee's of Co A or do they need to wait until the new plan year? Is there any holding period before Company C is required to offer any type plan to Company A ee's?

Thank you in advance for any help.