@westhigrad
Unfortunately, you really should do a spreadsheet with the calculation described by @Mike9241 (based on the Form 8937 - without the rounding used in the form).
Both IBM and Kyndryl can and may have future stock splits and spin-offs, mergers, and who knows what...all of which will affect the cost basis of future adjusted lots. NOT adjusting things now, is just looking for a headache down the road.
You "could" claim $0 for the Kyndryl on a sale... since that would result in MORE tax to the IRS. You cannot claim $0 if you gift any shares to a person while you live, as they must receive your actual cost basis. (You CAN claim anything you want as the basis [in principal - it is reported on a tax form though] if you gift to charity since the value on the date of gift is the charitable deduction regardless of cost basis.)
Similarly, you "could" claim the full basis of IBM on those lots still...but if you sold any IBM (or gifted it to a person and they sold it) - the IRS in an audit will find that you did not report a sufficient long term capital gain and will penalize you for that error.
"Zero sum tax events" from spin-offs etc do not mean that cost basis is not affected... it just means that there is no reportable income or gain (unless there is a tiny amount of cash received in lieu of fractional shares).
An advantage to holding your equities in a brokerage account is that the brokerage itself will compute all of this for you and your cost basis will always be up to date.
