If your company indicated that there was a cash value that you received as the result of the spinoff, or you purchased the spinoff shares, that value would be the basis.
If that didn't happen, you should have apportioned a certain amount of the AT&T basis to the Comcast shares, but that also didn't happen.
In this case, I agree with @pk, if you sold all of the 36 AT&T shares, and you took the full amount of the cost basis when selling those shares, the basis of the new Comcast shares will be zero.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
