How is Zakat calculated on goods and assets that grow daily, and how is their hawl (Zakat year) determined?

The trade goods are subject to zakat upon the completion of a full year (hawl) from the ownership of the nisab (minimum threshold) at which these goods were purchased. The goods must be appraised and combined with cash and expected debts. Then, the debts owed by the zakat payer should be subtracted. Zakat is then paid on the remaining amount. The nisab for banknotes is equivalent to 85 grams of gold, and the amount of zakat that must be paid is a quarter of a tenth (2.5%).