@qbteachmt Thanks for your valuable comments and insights and the two tax articles. TP has indicated that it was nonstatutory stock options (NSOs).

We will prepare form 1040-X and amend form 1040 by including the missing Schedule D and form 8949 with the gross proceeds and the cost/basis have the same value and the transaction is to be reported with Box B checked (Short-term transactions reported on Form(s) 1099-B showing basis wasn't reported to the IRS).  The total tax remains the same.

Appreciate it if you have further advice on this and thank you so much for your valuable time!