I have only two questions, all are concern to Zakaat Al-Maal. My first question is:
Somebody gave me a credit for the business. That money is my possession until one year I shall put the Zakaat for the profit that I got or all money I have? Because I shall pay the person who had gave me that credit.
My second question is:
I did the business about four years I did not put Zakaat, if I want put it know on this year how can I put it? I shall put for one year or all four years ago? Please explain me those two questions.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Whoever has a debt and has money and wants to pay Zakat on it, then one of the two following cases applies:

The first case: If the debt reduces the total amount to less than the minimum liable for Zakat and he does not have other money that is not liable for Zakat that could be used to repay the debt, in this case you do not have to pay Zakat on the money.

The second case: If the debt does not reduce the total below the minimum amount liable for Zakat, or one has other money that is not liable for Zakat that he could use to repay the debt, then he must pay Zakat on the money if it reaches the minimum amount liable for Zakat by itself or with other money added to it, or gold and silver, or tradable items provided a whole lunar year elapses on them.  Zakat has to be paid on the money and its profit altogether. The Zakat is 2.5% and the minimum amount liable for Zakat is the equivalent of the value of 85 grams of gold.

You mentioned that you were trading for the last four years, and did not pay the Zakat during those years; you have to pay the Zakat on each of those years when the Zakat was due. You have to calculate the Zakat on each year in a way to be on the safe side in order to be acquitted.

Allaah knows best.