"Elected S-Corp" means someone has to prepare the 1120S.

"The profit and lost are past through to the owner's 1040"

Then, shareholders get a K-1.

It seems your client is not Independent, but an employee of this S Corp. There should be Payroll and a K-1 for this business and their relationship to it.

You don't use the K-1 to prepare a Sched C for the same business activity.