Paying Zakah

My Question is regarding Zakah: 1) For example, let 1200 dollars be the minimum amount which makes one eligible to pay zakah. Should a person pay zakah on it as soon as it reaches that amount? 2) Assuming he has paid zakah on the minimum amount and after a few months he reaches that amount again, should he pay zakah again or is it sufficient for him to pay once in a year? 3) Or should the person wait for one year and calculate zakah ?

Praise be to Allah, the Lord of the Worlds, and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.       If you paid the Zakah, after you obtained some money, then you should wait a lunar year to be passed on this new amount. After passing a lunar year you have to pay its Zakah again. Suppose you owned 1200 Dollars in RAMADAN 1419 A.H. When the RAMADAN of 1420 A.H, comes you should pay 30 Dollars as Zakah from this amount. After five months,i.e., in a month of SAFAR, you gained 1000 Dollars, a new amount then you have to pay on this amount in 1421 A.H. in the month of SAFAR. Please refer to fatwa: 82016. You have to pay Zakah on your money with two conditions: 1-It should complete the Nisaab (the amount that determines when Zakah becomes obligatory) anyone who has more than this is obliged to pay Zakah) by itself or by gathering it with other earnings. 2 -One Islamic year (lunar) should be passed after possessing the money. Allah knows best.