A sole prorietorship is a disregarded entity; self and "company" are the same entity. That business activity is filed on Sched C which is part of the individual's Form 1040 tax return. A single-member LLC also is a disregarded entity and the same as sole proprietorship, for purposes of the Feds. LLC is a State construct.

Electing to be treated as an S Corp means there will be payroll and other entity change consideration issues (example: you don't take draws). The income tax filing for an S Corp is Form 1120 S. C Corp is Form 1120. HOA is Form 1120-H. These are entities independent of their shareholder-taxpayer owner. A C Corp pays its own taxes. A S Corp is a pass-through entity. A Partnership (multi-member LLC) files on Form 1065 and is a pass-through entity.

Note Form vs Schedule.

Hope that helps.