My Solo 401k Financial clients can use Charles Schwab to hold their self-directed solo 401k funds including the voluntary after-tax solo 401k funds. They may then also convert the voluntary after-tax solo 401k funds to their  Charles Schwab Roth IRA.  This is all possible because My Solo 401k Financial not Charles Schwab offers a solo 401k plan that allows for voluntary after-tax contributions in addition to the conversion of voluntary after-tax solo 401k funds to Roth IRAs.

Video Slides:

Mega Backdoor Roth Solo 401k Conversion to a Schwab Roth IRA

Schwabs Form for Moving the Funds from the Voluntary After-Tax Solo 401k to the Schwab ROTH IRA

To view Schwab’s Form CLICK HERE.

COMPLIANCE NOTE:

Conversions are reported in the year that the funds are actually moved over to the Roth account. 

The solo 401k contribution rules are different from the  conversion rules. Contributions can be made by your business tax return due date plus any timely filed extension for the prior year.

In sum, the voluntary after-tax solo 401k conversion will be nontaxable regardless if  you convert the after-tax contributions that were made in 2025 or in 2026 for 2025.

My Solo 401k Financial On-Line Conversion Form for Issuing Form 1099-R

After you have Charles Schwab convert the solo 401k voluntary after-tax funds to the Roth IRA also held at Charles Schwab, the next step is to log the conversion our website using the following link: https://www.mysolo401k.net/after-tax-solo-401k-to-roth-ira-conversion-form/

We, (not Charles Schwab) will then issue the Form 1099-R by February of 2027 to report the 2026 voluntary after-tax conversion to the Roth IRA.