Is the price of the truck and the trailer to be deducted from the money on which a year has passed when calculating zakat, or is the amount of the trailer to be added to the money on which zakat is due, knowing that the payment for the trailer was delayed beyond the date zakat became due?

Zakat is calculated according to lunar months, not solar months. If the wealth reaches the nisab (minimum threshold) and a full lunar year passes over it, Zakat becomes obligatory. Newly acquired wealth is subject to Zakat upon the completion of its own hawl (one lunar year). Any amount spent from it during the year is not deducted from the obligatory Zakat amount. As for deducting the price of the locomotive that was not delivered to the selling company, the contract is invalid because it is a sale of debt for debt, which is the prohibited sale of al-kali’ bi al-kali’. Therefore, the money is owned by you and Zakat is obligatory on it. However, if the sale were valid and the debt settled upon you, there is a difference of opinion among scholars regarding the issue of deducting debt from Zakat.