What is the amount due as Zakat on money collected for building a house, from which a down payment has already been spent on building supplies?

Money acquired from non-growing capital is subject to zakat (definition) on each installment upon the completion of its individual hawl (lunar year), and this is the preponderant opinion of the majority of scholars. The amount of zakat due on acquired funds is calculated upon the completion of the hawl specific to each amount. For instance, ten thousand [currency unit] acquired in Dhul-Qa'dah 1428 AH will have its hawl completed in Dhul-Qa'dah 1429 AH, and its zakat will be 250 euros. As for the nine thousand [currency unit] acquired in Rabi' al-Akhir, if only three thousand euros remain when its hawl is completed, its zakat will be 75 euros. The amount acquired in Dhul-Qa'dah 1429 AH will have its zakat due in Dhul-Qa'dah 1430 AH. As for the view of Abu Hanifa, he holds that acquired money is subject to zakat upon the completion of the hawl of the original capital, by combining what has been earned and subtracting what has been spent, then paying zakat on the remainder.