Two Conditions for Nisaab

The Nisaab will not be valid unless it fulfills two conditions:

1) The amount that has reached Nisaab must be the excess or surplus known as "faadil" from one's essential needs such as food, clothing, housing, vehicles, tools and machinery that is used in business. The essentials for living are exempted from Zakat.
Although what constitutes nisaab may change from one country to another, the amount that is needed for the basic needs of living in different countries is very similar, because the market place determines the prices, whether it is an official market or a non-official market. In the poorest countries people do without or live below the poverty standard, and that is why many go hungry or without basic essentials.
However, we must realize that Zakat is an act of worship (ebadah) like Salaat. The element of intention (niyyah) is necessary, and we should not overly rely on state agencies to determine for us the requirements of our religious duty. The so called the "consumption basket" (that is poverty level as determined the social security administration which are updated every fiscal year) may not be the same as what Islam considers minimum Nisaab.
In the industrialized countries, the consumption basket may include items that are not necessarily essential, such as entertainment, extra clothing, variety of food, eating in restaurant or eating at home, owning more than one car as opposed to having three cars in the driveway, drinking water as opposed to juices, eating regular food or special "health" food. This is why I believe it is essential that we do not lose site of the fact that Zakat is ebadah of wealth, like salaat and fasting. Non Muslims may consider all the things mentioned above as essentials while Muslims will not. Indeed, no Muslims in good standing will attempt to hide behind the label of consumption basket so as to evade Zakat.
Nisaab eliminates the possibility of injustice or unfair treatment of the Zakat payer. To suggest that if we do not follow the rules of International Monetary Fund or the arbitrary figures of social security administration or department of agriculture we will be doing injustice to the Zakat payer is ludicrous.
2) Nisaab must mature, that is the money is not liable for Zakat unless it has remained a full year in the possession of a person. This is the understanding of the majority of the scholars. Imam Abu Hanifah (R.A.A) said: "What should be considered is the existence of nisaab at the beginning and the end of the Zakat year set by the payer". It does not matter if the nisaab money increases or decreases during the calendar year, as we will explain later.
This condition does not include farm produce, for it is due on the day it is harvested. Allah (SWT) stated: "... But render the dues that are proper on the day that the harvest is gathered..." (Al-Qur'an, 6: 141) According to Imam Al-`Abadi, (R.A.A) Zakat money is of two kinds: one that by its nature can not be invested and Zakat of this category is due on the day of harvest. This includes all the farm produce that is liable for Zakat. The other is wealth that can be invested in the hope of a good return, like cash, gold or silver, because the opportunity is there that cash in one's hand can be invested for a good return. This includes currency investment, merchandise and livestock. Their Zakat is not due until they have matured in one full year.
The proof of this condition is the Hadith related by Ibn `Umar that the Messenger of Allah (S.A.W) said: "He who acquires property is not liable for Zakat on it till a year passes." According to Ibn Rushd (R.A.A) this is the understanding of the majority of scholars, including the four rightly guided Khalifahs.