How does a man pay zakat if he has fluctuating money in the bank, goods, debts owed to him by others, and company shares, knowing that his balance may sometimes reach zero?

The method for calculating Zakat (definition) on trade goods, including stocks, is by assessing their market value at the end of the Zakat year (Hawl), adding cash and collectible debts, and then subtracting outstanding debts. If the remaining amount reaches the Nisab (definition) (minimum threshold), then one-quarter of one-tenth (2.5%) becomes obligatory as Zakat. As for uncollectible debts, Zakat is not due on them until they are collected, and then only for one year. A condition for deducting debts is that the Zakat payer must not possess other non-Zakat-eligible assets sufficient to cover the debt. Scholars have agreed on the requirement of the Nisab for trade goods at the end of the Hawl, but they differed regarding the rest of the Hawl. The Malikis and Shafi'is hold that the value at the end of the Hawl is the determining factor, while the Hanafis and a second opinion among the Shafi'is consider the value at both ends of the Hawl. In contrast, the Hanbalis and a third opinion among the Shafi'is consider the value throughout the entire Hawl.