Zakat

The Zakat is a personal duty (Fardh ‘Ayn) on every Muslim who possesses the minimum amount (Nisab) in excess of his debts for the duration of a year. Whenever it becomes obligatory upon the wealth of a Muslim, it cannot be abolished. Its collection is independent of the State's needs or the Ummah's interests unlike the tax funds, which might be collected from the Ummah only in cases where there are no funds in the Bait ul-Mal to meet the State's needs and the Ummah's interests. Rather it is the right of the eight categories that the State must deliver to the Bait ul-Mal whenever it becomes due, whether there is a need for it or not. Zakat is not of the rights of the Bait ul-Mal nor is it a beneficiary from it. It is a right of the eight categories specified by Allah in the Ayah

"Verily the Sadaqah is only for... " [At-Tauba: 60]

The Bait ul-Malis only a place of sanctuary for it, such that the Imam will spend from it to those specified by the Ayah according to his view and Ijtihad.

Zakat is obliged upon the man, woman, child and insane person due to the general form of the sound Ahadith that oblige Zakat without restriction.
Amru bin Shu'aib narrated from his father from his grandfather he said: "The Prophet preached to the people and said: 'Verily, whoever has charge over an orphan with wealth then let him invest it. He should not leave it to be eaten by Sadaqah.'"
From Anas (in a Marfu’ narration): "Trade in the orphans' wealth (so that) Zakat does not consume it."
Qasim bin Muhammad said: "Aisha used to invest our wealth, as we were orphans, and give Zakat from it."
Malik bin Anas considered that there was Zakat on the lunatic's wealth, as did Az-Zuhri. From ibn Shihab: "That he (pbuh.) was asked about the lunatic's wealth, is there Zakat upon it? He (pbuh.) said: 'Yes.'"

Zakat is obliged on the following properties:
1.Livestock including camels, cows and sheep,
2.Crops and fruits,
3.Currency,
4.Trading goods and merchandise.

Zakat is obliged on these properties if they reach the Nisab for the duration of one year except for crops and fruits whose Zakat is due the moment they are harvested.