At what age does a Muslim become responsible for the zakat on his wealth, and who pays zakat, and how is it calculated?

The conditions for the obligation of zakat are three: complete ownership, the wealth reaching the [nisab] threshold, and the completion of a full year [hawl]. Zakat becomes obligatory on a specific Muslim's wealth if these conditions are met. It must be paid by the one upon whom it is due if they are an adult. If they are a child or insane, their guardian is responsible for paying it. If zakat was not paid when it became due, the owner must pay it for the previous years of obligation upon reaching adulthood.