Is zakat obligatory on a sum of money held in a stock portfolio after the market collapse, and is the portfolio owner liable for the shareholders' money, and what is the ruling on issuing a bank guarantee for a sum of money?

1. The zakat obligation for the portfolio is directed to the owner. The speculating partners (mudaribs) pay zakat on their share if a hawl (lunar year) passes over it. As for the working partner (amil mudarib), he is only obligated to pay zakat on his share if he has one. The obligation of zakat does not change due to the owner's inability to extract it, or his not owning money outside the portfolio, or any losses incurred, as long as it reaches the nisab.

2. If the working partner (amil mudarib) was authorized to manage the money and did not commit any negligence or transgression, then he is not liable for the loss. Experts in the field determine this. There is no liability on the worker for the damage or partial damage of the money unless it was due to his transgression. As for a bank guarantee based on a percentage, that requires further detail.