Improperly excluded employees

Does anyone have the prescribed method for mandatory employee contributions that were missed due to improper exclusion from the plan.  While it is clear how to correct the employer contribution, it is not as clear if the employer is to pay the missed employee contributions as well.  Apply the same method as missed opportunity for after-tax contributions under EPCRS?

I 'think' the employees may be able to write a check for this one.  I know that elective deferrals must be made from compensation that has not yet been received.  I don't believe that same standard applies to after-tax [under Section 401(m) ].  This is just an initial thought.

Good Luck!