I realize now that you stated this was SMLLC in the original question text.

You seem to have the following:

Your client doesn't seem to have a situation of "changed to." Don't "read ahead" to something that doesn't apply.

Your client, a SMLLC, wanted to form a corporation, and has done the Entity Name and FEIN paperwork. The corporation is not registered for payroll under State or Federal. It's not in business, yet. You are describing a new entity has been created and has not yet operated. There has been no startup for the corporation. It is a "shell."

Your client would file Sched C for 2019. Your client would not have been paid through payroll. Only the employees are paid through payroll.