I'm still questioning whether you have actually made an excess contribution or if you are just misusing terminology. Your solo 401(k) contribution is based on net earnings, not your net income. Net earnings are net profit from self-employment minus the deductible portion of self-employment taxes. Are you saying that your net profit from self-employment is near zero? (It's entirely possible to have net profit sufficient to make a $19,500 Roth 401(k) contribution and still have enough non-business deductions to bring your net income to near zero. The non-business deductions have no effect on the amount that you are eligible to contribute to the Roth 401(k).)
