A worthless stock is part of my inheritance. Any tax value?

Probably not to you. It could have been declared on the fiduciary return by the estate (assuming the estate is large enough to file a fiduciary return).

The stock assumes the FMV at time of death, which was probably zero. That means you cannot dispose of the stock and get a capital loss.

Probably not to you. It could have been declared on the fiduciary return by the estate (assuming the estate is large enough to file a fiduciary return).

The stock assumes the FMV at time of death, which was probably zero. That means you cannot dispose of the stock and get a capital loss.
The stock is part of an account which is joint with the right of survivership. We think of it as inherited because my then 88 year old mother originally made the investment. (I am brand new to this posting stuff so I asked a very general question, initially.) Does this change things? The account was changed to the joint account before she died at 94.

Even if it's a joint account, it's STILL her stock. My original answer applies.