Unfortunately, you can't do that. The election to have an LLC treated like an S-Corp or C-Corp must be made at the time the LLC is established/open, or within a short timeframe (60 days I think) after that. Since your intention is to dissolve the LLC by the end of 2021, it makes absolutely no sense to want that anyway. If you could do it, you'd just be creating unnecessary paperwork and costly filing requirements that will have little (if any) benefit to you at all. Just report the business income/expenses on SCH C as a part of your personal 1040 tax return indicating that you both opened and closed/disposed of the business in 2021, and be done with it.
