A Solo401k can accept rollover from qualified retirement plans, including Traditional-IRAs, SEP-IRA, as well as 401k, Profit-Sharing, Defined-Benefit or any other employer-sponsored plans from past employer. The rollover will be tax-free for a Solo401k, therefore you can maintain your wealth in this seamless transition. Rollover-funds will go to a pre-tax portion of your Solo401k. Keep in mind that a Solo401k cannot accept rollover from a Roth-IRA. Roth-401k however can be rolled-over into Roth Solo401k. If you wish to do a Roth-conversion, you can do so after completing the rollover.