Thanks a lot , am I correct if so one S Corp can have two method; one for MTM and the other for routine activities or client should have one S Corp just for MTM, day trading along with its election.

For sole proprietor, will file on schedule C without SE tax, right, so how did you make your client exempt from SE tax since we have two lines on sch C which belong to forms 4029 and 4361 above the first QuickZoom on schedule C. 

 For sole-prop; he started trading in the beginning 2022 and already filed his 2021 return.  When he should file 3115? As I understood you explained and my searching form 3115 should file before April 15, 2022 for the year of 2022 trading, am I right? If so, what is the solution? Again, I really appreciate for your help.