The fact that you took possession of the land with the intention of selling it means that zakaah is due on it every year, so you should calculate the value of the land at the end of the year and pay zakaah on this amount. The rate of zakaah that must be paid on it is one-quarter of one-tenth, i.e. 2.5%, which should be paid in the ways specified by Allaah in the verse (interpretation of the meaning): 

“As-Sadaqaat (here it means Zakaah) are only for the Fuqaraa’ (poor), and Al-Masaakeen (the poor) and those employed to collect (the funds); and to attract the hearts of those who have been inclined (towards Islam); and to free the captives; and for those in debt; and for Allaah’s Cause (i.e. for Mujaahidoon — those fighting in a holy battle), and for the wayfarer (a traveller who is cut off from everything); a duty imposed by Allaah. And Allaah is All-Knower, All-Wise”

[al-Tawbah 9:60] 

It should be noted that if goods for trade are bought with gold, silver or cash money (riyals, dollars or other currencies), or in return for other goods (barter), then the year for calculating zakaah starts from the time when you acquired the wealth with which you paid for the goods. Based on this, then the year for the goods does not start from the time you took possession of them, rather it starts from the time you acquired the wealth with which you paid for them. 

For example: if a man takes possession of one thousand riyals in Ramadan, then he starts the reckoning of the year. Then in Sha’baan of the following year (i.e., one month before the year ends) he buys some goods for trade with this thousand, then he should pay zakaah on these goods in Ramadaan, in other words just one month after he took possession of them. That is because the year for these goods is based on the year for the money with which they were bought.  

See al-Sharh al-Mumti’, 6/149, by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him). 

It says in Fataawa al-Lajnah al-Daa’imah, 9/331. 

Zakaah is due on land that is prepared to be bought and sold, because it comes under the heading of trade goods, and thus is included in the general meaning of the texts of the Qur’aan and Sunnah which state that zakaah is obligatory, such as the verse (interpretation of the meaning): 

“Take Sadaqah (alms) from their wealth in order to purify them and sanctify them with it”

[al-Tawbah 9:103] 

And Abu Dawood narrated with a hasan isnaad that Samurah ibn Jundub (may Allaah be pleased with him) said: The Messenger of Allaah (S) commanded us to pay zakaah on whatever we had prepared for sale. This is also the view of the majority of scholars, and it is the truth. 

The Standing Committee was asked: 

With regard to lands that are bought for the purpose of selling, how should we calculate them when we calculate zakaah – should we base it on the price for which we bought them or on the market value at the time when the year for zakaah has passed? 

They replied: 

Lands that are bought for the purpose of selling come under the heading of trade goods. The general principle in Islamic sharee’ah is that trade goods are to be calculated upon the completion of one year at market value, regardless of the price for which they were bought, whether that was more or less than the market price at the time when zakaah becomes due. The zakaah should be paid from their value. The rate of zakaah is one-quarter of one-tenth. So for land worth one thousand riyals, for example, the zakaah is twenty-five riyals, and so on. 

Fataawa al-Lajnah al-Daa’imah, 9/324, 325. 

With regard to the nisaab for zakaah, as previously stated in question no. 42072, the nisaab for zakaah on gold is twenty dinars i.e., 85 grams of gold; the nisaab for silver is two hundred dirhams, i.e., 595 grams of silver. 

The nisaab for money (i.e., Saudi riyals or other currencies) is whatever reaches the value of the nisaab for gold or silver. As the value of silver is now less than that of gold, the nisaab for money now is the equivalent of 595 grams of silver. 

And Allaah knows best.