Hello-

Schedule C Owner with $30K net Schedule C. Wife works in business and gets small W2 but no other employees. Husband has already maxed out pre-tax 401k through an unrelated employer. If they set up a Solo 401k with a provider that offers after-tax contributions, how much after-tax contribution can they make (for Mega Backdoor Roth)?

1. Can husband go up to 100% of net Schedule C compensation ($30K) via voluntary after-tax contributions?
2. Can this be done for 2024 even if the Solo 401k is setup up now?

Thank you!