How is the value of Zakat calculated, and what is its method for profits resulting from free trade (such as selling cars, phone numbers, and electronics)? Is it annual, monthly, or weekly?

Zakat is calculated on gold, silver, currencies, and trade goods at a rate of 2.5% after the passage of a lunar year from the time of possessing the nisab. Zakat becomes obligatory on the principal capital and its profit together. It is not a condition for the profit to complete a hawl (year) because it is subordinate to the principal capital. Therefore, if the total of the principal capital and profits reaches the nisab at the end of the hawl, Zakat becomes obligatory on both of them in full. It is permissible to dispose of the profit and principal capital before the hawl, but not after it until the obligatory Zakat is determined and disbursed. Zakat does not need to be deducted from the profits until the hawl of its origin (the principal capital) has commenced.