If you are involved in purchase and sale of raw properties and making profit through such sale transactions, then this would tantamount to Trading Business (Retail Business) in which case only Zakat on weath at year-end will be applicable (Total Zakat would be 2.5% of cash-in-hand plus cash-in-bank plus value of stock-in-hand which would be value of properties in this case). However, if one is engaged in construction and sale of such houses on those properties, then one would be required to pay both Zakat on Production and Zakat on Wealth with a difference that land in such cases will be exempt from Zakat, being a mean of production and zakat on production will be applied on the actual production i.e. house built on the land. Zakat in such cases can be given on the gross production value or on value addition which is to be decided by the state but in the absence of any state regulation, one should make an informed decision in this regard considering the nature of raw materials being used and their significance in the production process.

To understand these heads and how to calculate Zakat in each head and when is Zakat due on each head, please refer to the following thread and take your time in reading and watching each response. Please do ask a follow-up question in case of any difficulty.

Discussion 58129

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For short comments of Ghamidi Sahab, please refer to the video below from 1:10:53 to 1:12:56

https://youtu.be/cQn9tcHEoq8?t=4253