Overfunding Safe Harbor Contribution can use classify as "mistake

[Guest Kelly Musico]

We have a client that is a partnership. The plan is a 401k Safe Harbor Plan. The plan limitation of 15% is exceeded by deferrals and the 3% safe harbor contributions only. Can you return the excess amount to the employer and classify that amount as a mistake in fact? Or do you blow them into the IRS on a 5330? We're thinking we have to report the excess amount as the safe harbor contribution is required?!