S Corp, sole prop, how do I charge ss tax on form?

Susan was nice and didn't tell you Paul Harvey's the Rest of the Story.  Now you need to tell the business owner that they need to go back and file delinquent payroll tax returns for those "draws" that they took out during the year and make those late payroll tax payments for the year.

"to fill out K-1 for 1040 form to go to sch c"

This is what is confusing. What you described here is translated as: The person who is a Shareholder in an S Corp has a separate sole proprietorship business.

What they cannot be is an Independent Contractor (Sched C operation) to their own Corporation that they work for (S Corp). Because, if they already work for that Corporation, that makes them an Employee.

Are you able to guide this person, or perhaps you also need a mentor to help both of you? That's how you learn what the different entity types means to your taxpayer and how to manage them both financially and for tax reporting.

For instance, did you try to enter this person's personal vehicle business mileage as part of the Sched C? Because that is an example of something they would submit to their employer for reimbursement under An Accountable Plan. There is no Business Mileage deduction for an employee on their own tax return. There is not even a Sched C, unless you are telling us this person has one Job and one Business?