Hi and welcome to Just Answer!
The basis of shares for capital gain determination is the fair market value at the time the aunt died. Because the property was acquired via inheritance - there is a stepped up basis.
Let me know if you need any help or clarification.
Thank you for your response. I knew as much.
The issue that has been raised is as follows: since the shares, which were in the trust of the grandfather, were aggregated with the free estate of the aunt is the basis price that of the grandfather or the value of the shares as at the time that the aunt died.
If you client became an owner of these shares any different way - not as inherited - that we need to know - if that was a gift, purchase, or any other way. Depending on that there might be different determination of the cost basis,
According to your information - your client acquired shares from the aunt as a result of her death - thus via inheritance. Stepped up basis for inherited property is generally determined as a the fair market value at the time the decedent died.