We have a client that was a 2 person partnership, an LLC, which filed form 1065 for the 2019 tax year.  At the beginning of 2020 one of the partners broke away, but continued to receive money from the company as a subcontractor.  The company issued them (or rather, issued to their new company) a 1099 for all the money they received in 2020.

Does anyone have any advice on how to transition this company from a two person partnership to a sole proprietor (one person owner)? and which form(s) to file?