@SLYKTAX , sorry that I provided info that you already you knew -- please forgive.
You wrote --> " Choosing another basic maybe better than I had chosen at the time I sold a security"
Thus you have chosen a basis -- you would be at risk of perjury if you now claim a different basis than what you told your broker at the time of the transaction . Please consider contacting your broker as to which lot he/she sold the shares from.
