A solo 401k from My Solo 401k Financial allows for the conversion of voluntary after-tax solo 401k funds to the Roth solo 401k. For client’s who use My Solo 401k Financial as the solo 401k plan document provider and use Schwab as the brokerage firm to hold the solo 401k funds, the voluntary after-tax solo 401k funds can be converted internally within Schwab to the Roth solo 401k.
Using Schwab’s Form To Internally Move the Voluntary After-Tax Funds to the Roth Solo 401k Funds
To logistically transfer funds electronically from the voluntary after-tax solo 401k plan brokerage account to the Roth solo 401k plan brokerage account, fill out the Schwab form titled “Move Assets from My Schwab Brokerage Account.” Click Here to download their form. Alternatively, you can use the “Move Money / Online Transfer” option on the Schwab website, and if you use this method, please be sure to let us know about the conversion once it has occurred: Voluntary After-Tax to Roth Solo 401k
Submitting the Form to Schwab for the Conversion of the Voluntary After-Tax Solo 401k Funds
Return the completed form by using Secure Messaging on Schwab.com or SchwabAlliance.com or Fax to Schwab at 888-526-7252.
Our On-Line Conversion Form
After you have Schwab transfer the funds, the next step is to log the in-plan conversion on our website using link below: After-Tax to Roth Solo 401k In-Plan Conversion Form: https://www.mysolo401k.net/after-tax-to-roth-solo-401k-in-plan-conversion-form/ After you log the amount on our website, we will have the information we need to prepare 2026 Form 1099R. We provide 2026 Form 1099R to clients by the end of February of 2027.
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.
