Is it Islamically permissible to deduct a sum of money that was paid to reserve a plot of land in a lottery, considering it a debt owed by the zakat payer when calculating the zakatable amount, knowing that the sum was later refunded? And how can this error be corrected if it exists?

The amount paid to reserve the land is included in the total wealth subject to zakat. The fact that it is held by the Ministry of Housing does not remove it from the ownership of the zakat payer, and therefore does not prevent the obligation of zakat. This is the view of the majority of scholars, by analogy with mortgaged property. Accordingly, zakat is obligatory on this wealth.