As I’ve mentioned in my SEP IRA versus Solo 401(k) comparison, the problem with the additional paperwork involved with a 401(k) is that you have to find an administrator that is willing to do it for you at minimal cost. Compare that with the SEP-IRA, you can usually walk up to many brokers, open up an account, and start trading anything with no annual fees and just commissions.

For example, I opened up my SEP-IRA last year with Vanguard, but I can’t open up a Self-Employed 401(k) with them directly as they won’t be my administrator. The only option I found was to go through a third-party administrator like 401kBrokers, which charges an annual maintenance fee of 0.25% of the account balance. I think the fees ...