If just one participant will process the mega backdoor Roth solo 401k conversion (i.e., the conversion of voluntary after-tax funds to the Roth solo 401k), then at least two brokerage accounts are required (one to hold the solo 401k voluntary after-tax contribution, an a second one to hold the Roth solo 401k funds).

Choose the Brokerage Account Firm

If you have yet opened the necessary brokerage accounts to process the mega backdoor solo 401k conversion, please click on the applicable brokerage firm name for information surrounding opening the brokerage accounts: 

Fidelity | Schwab | E-TRADE | TD-Ameritrade