A Solo 401(k) can accept rollovers from many retirement plan types. Firstly, funds must be eligible for rollover. Most any IRA may be rolled over at any time. A 401(k) or similar employer retirement plan from former employment can be rolled over. A current employer retirement plan may not be eligible for rollover. Any tax-deferred retirement plan such as an IRA, SEP IRA, or old 401(k) may be rolled into the Solo 401(k). The Roth portion of a prior employer 401(k) may also be rolled. A Roth IRA may not be rolled into a Solo 401(k). Learn more.