How is the Zakat calculated for a man who works in trade, buying and selling, and whose daily income is 1000 Liras, if the nisab was reached on Shawwal 20? Does he pay Zakat only on the amount of the nisab on the same date after a year has passed, or does he recalculate his money anew and wait a full year for it?

A man must know, by the Hijri date, when his money reaches the nisab (definition). The nisab is approximately equivalent to 85 grams of pure gold or 595 grams of pure silver. If his money and the value of his trade goods reach the nisab and do not fall below it throughout the year, zakat (definition) becomes obligatory upon him when a full year has passed. If he acquires additional wealth during the year, and it is profit from trade, it is added to the original capital and zakat is paid on both together. If it is from another source, such as inheritance or a gift, zakat is paid on it when its own year passes, or it can be added to the original capital, and zakat is paid on all of it at the same time.