Is Zakat now due on a loan that was fully disbursed after three years, with its amount decreasing each year?

Saved money is subject to Zakat if a year has passed over it and it reaches the nisab. If it is difficult to ascertain the exact amount each year, then exerting effort and investigating to the best of one's ability is sufficient. If the muzakki (person paying Zakat) has a debt, he should deduct an amount equivalent to the debt from his balance each year. If, after settling the debt, the remaining amount reaches the nisab, Zakat becomes obligatory. The nisab for banknotes is approximately equivalent to 85 grams of gold, and one-quarter of one-tenth (2.5%) must be given.