I don't understand. In your original post you said "I did capital gains for stock" so I assumed you knew the basis of the stock sold. Is that not the case? What did you mean by that statement?
If you don't know the basis for stock purchased over 25 years ago through and employee stock plan - an ESPP? - it would be extremely difficult to come up with a reasonable basis at this point. You can make some sort of estimate I suppose but it has to be one that the IRS will accept, if they ever ask. Perhaps the 25-year ago numbers are small enough that $0 for the basis isn't too far off?
