Is Zakat due on the amount of the Nisab, or on the amount exceeding the Nisab?

Zakat becomes obligatory on wealth if it reaches the nisab (minimum threshold) and a hawl (full lunar year) passes over it. It becomes obligatory on the entire nisab and any excess amount, provided the conditions are met. Zakat is not obligatory on newly acquired wealth after the nisab is complete until a hawl passes over it. It is permissible to pay it in advance along with the nisab wealth.