Has anyone done a late S-Corp election in order to supersede a more recent S-Corp election? 

New client to me (small construction business - Sched C) always self prepared his taxes.  He filed for S-Corp election on his own and obtained effective start date of 01/01/2025. 

I'm working on his 2024 and he definitely could benefit from making a late election effective 01/01/2024.  Potential savings of $18K+.  My research does not give me conclusive results on whether I can make a late election even after having received a newer effective date.

Thanks