Solo 401Ks were particularly designed to serve the needs of small businesses which employ only the owner or the owner and his or her spouse. Since the overwhelming majority of small businesses in the U.S. are in this category, most startups are ideal candidates for a Solo 401K.
A Solo 401K is set up and administered in an entirely different way from a traditional 401K. And compared to traditional 401Ks, 503Bs, and the more familiar types of IRAs, a Solo 401K gives you much greater control of your retirement funds and increased flexibility as you invest them.
What sets a Solo 401K apart from any other instrument like it is the absolute and total control that you have over your funds. Your company, through an affiliated trust fund which it creates, is the custodian of your Solo 401K funds. And you personally serve as the trustee. This means that you have neither the expense nor the cumbersome rules of a bank or brokerage house being the custodian of your funds.
You have complete control of where your money is invested and when it is invested. There are no outside approval loops to go through. And if you already have other retirement programs, you can roll them all over into your Solo 401K so that you have this level of freedom and control over all of your retirement funds.