En principio los porcentajes para el Cost basis los darán cuando publiquen el IRS Form 8937 antes de finales de Noviembre, tal como dicen en el siguiente enlace: link
How is the cost basis of my IBM shares affected by this distribution, and what is the cost basis of my Kyndryl shares?
IRS Form 8937, Report of Organizational Actions Affecting Basis of Securities, provides information about the basis consequences of the distribution and how to allocate your cost basis between the IBM and Kyndryl shares. A copy of the form will be posted to this site before the end of November.