Is zakat obligatory on a piece of land that the father verbally relinquished to his son in the presence of witnesses, while it officially remains in the father's name? And how is its zakat calculated? Is its zakat obligatory retroactively?

If a father gifts a piece of land to his son with the consent of all the siblings, there is no objection to accepting it, and it becomes his property upon taking possession; for a gift is not owned except by taking possession, according to the majority of scholars. This land is not subject to zakat (definition) unless it is prepared for trade. If it is prepared for trade, its owner must appraise it at the end of each year (hawl) and pay two and a half percent (one-fortieth) of its value as zakat.