Aslam Al Akham
If one has us$ 10,000 above the nisab at the beginning of the Zakat year and by end of that year he earns another Us$ 5,000. Therefore making it US$ 15,000 . But the extra 5,000 have not been in his possession for a full zakat year. Is the Zakat then payable on the 10,000 only or on 15 ,000.
It is not obligatory that zakat be paid on wealth until after the year ends. This refers to the $10,000. That is unless the additional money, which has come after the beginning of the year is a result and proceeds from the original money. This would make this money have the same zakat status, and you would then have to pay zakat on the entire $15,000.