safe harbor contribution change mid year

[KevinMc]

A company with 30 employees has a non elective safe harbor contribution of 3%.  They would like to change to a safe harbor match with a 4% match (or using the match formula).  Can this change be made anytime with participant notice or must it be done at the beginning of the next plan year with participant notice?  If it can be done during the year:  what kind and how much of a notice do the participants need to be given.  Thanks for any help!

[Lou S.]

Next Plan Year.