Solo 401k or Individual 401k is for maximum of 2 individuals

Besides only being available to the self-employed,  if you want to  open Solo 401k maximum of two individuals can participate.

Generally when two participants participate in same solo 401k plan, it is usually both spouses or both business partners. However, to participate each participant must separately generate self-employment income from same business. Therefore, if only one spouse or business partner generates self-employment income, only that spouse can participate in solo 401k.

Separate Checking Accounts Necessary--one for each participant 

If both individuals qualify for same solo 401k plan and decide to open solo 401k, separate checking accounts are necessary for each participant. Subsequently each participant transfers/rollovers other IRAs or retirement plans to his or her respective sub account/checking account.

Here's how checking accounts would be titled

For example, let's say Jan and Jim Everest are both self employed through same company and decide to open solo 401k (ABC Solo 401k Trust) 

As a result, two checking accounts--one for Jan and another for Jim--would need to be opened.

The the title for each Solo 401k checking account  would read as follows:

Checking account 1 for Participant Jim: ABC Solo 401k Trust, Jim Everest, Trustee

Checking account 2 for Participant Jane: ABC Solo 401k Trust, Jane Everest,Trustee