Unlike an IRA account, there is no custodian required for a Solo401k. Plan participants can choose to act as the trustee of the plan and assume full control over their retirement funds. Solo401k with Checkbook Control allows you to complete transactions as easily as writing a check. Checkbook control offers a few benefits: You don’t have to get approval from your custodian for any investments. This means there is no custodian fee. There will be no delay either, so you will be able to act fast and capture investment opportunities quickly.