How is zakat paid on cars sold by installment, knowing that some buyers delay payments, and there is no liquidity available when the hawl is due?

Cars designated for trade are subject to zakat if a year has passed over them and their value reaches the minimum threshold (nisab) either on their own or when combined with cash or other trade goods. These cars are to be valued at the end of the year, and a quarter of one-tenth (2.5%) of their value is to be paid in cash, not from the cars themselves.