Yes.

Any reference you can point me too?  All I can find is the employee side.

NEVER MIND I FOUND IT.  THANKS FOR RESPONDING IT GAVE ME THE PUSH TO LOOK FURTHER.  ACTUALLY FOUND IT RIGHT ON THE IRS WEBSITE.

Example 1: In 2020, Greg, 46, is employed by an employer with a 401(k) plan, and he also works as an independent contractor for an unrelated business and sets up a solo 401(k). Greg contributes the maximum amount to his employer’s 401(k) plan for 2020, $19,500. He would also like to contribute the maximum amount to his solo 401(k) plan. He is not able to make further elective deferrals to his solo 401(k) plan because he has already contributed his personal maximum, $19,500. He would also like to contribute the maximum amount to his solo 401(k) plan.

Greg is not able to make further elective salary deferrals to his solo 401(k) plan because he has already contributed his personal maximum, $19,500, to his employer’s plan. However, he has enough earned income from his business to contribute the overall maximum for the year, $57,000. Greg can make a nonelective contribution of $57,000 to his solo 401(k) plan. This $57,000 limit is not reduced by the elective deferrals Greg made under his employer’s plan because the limit on annual additions applies to each plan separately.