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@TaxStyle wrote:

My client set up a company because people advice her to, but she wasn't clear about whether it is an S corp or C corp when I talked to her.

So later I found out it is an C corp when i prepared her 2020 return, and she is the sole owner and the only member of the C corp. However, her 2019 return (initial return) was filed using S corp form 1120-S. 

Take a step back.

What type of taxation do YOU think is best for her situation?  S-corporation?  C-corporation?  Sole Proprietor?  Something else?

You said the client set up a "company".  What does that mean?  Is it a corporation?  Or is it something else, such as an LLC?  It it was an LLC (or something similar), was an election filed with the IRS to tax it as a C-corporation?

Has 2020 already been filed as a C-corporation?  If not, and *IF* S-corporation is optimal, it seems like filing a late S-election may be applicable.   But I think 2020 has already been filed as a "C", it would mess up the ability to file the late S-election.