No. However, if you do not make elective deferrals (employee contributions) to your regular employer retirement plan, you can open a solo 401 (k) plan and contribute your net profit from self-employment minus half your self-employment tax. This deduction is reported on Line 28 of Form 1040, and has no impact on your self-employment tax.
If you do make elective deferrals (employee contributions) to your employer plan, the maximum of your elective deferrals across all such plans is $18,000 ($24,000 if you are over age 50). Your profit-sharing contribution on the solo 401 (k) is unaffected by this.
