I have a self-employed, highly compensated sole proprietor (no employees) who is considering options to shelter income. He currently has a MPP and a SEP IRA.

It appears an individual 401k would allow him to shelter more (55 years old). However, I’m not familiar enough with the down side.

A SEP is fairly straight forward, but doesn’t the MPP and the indiv 401k require “employer” filings if they grow past a certain asset size? What are these filings?

Thanks