How are the zakat threshold (nisab) and its value determined for business profits that are received in installments rather than in a single payment?

The nisab (threshold) for Zakat on money is 20 gold dinars (approximately 85 grams of pure gold) or 200 silver dirhams (approximately 595 grams of pure silver). If each partner's share of trade goods reaches this nisab, Zakat becomes obligatory. Trade goods must be combined with cash, and if the combined total reaches the nisab, Zakat is due on it. The amount that reaches the nisab is subject to Zakat every lunar year by paying a quarter of a tenth (2.5%). As for outstanding installments, if they are owed by a solvent debtor, they are subject to Zakat along with one's wealth every year, or upon their receipt for past years. If the debt is owed by an insolvent, procrastinating, or denying debtor, Zakat is not obligatory on it along with one's wealth. Its owner pays Zakat on it upon its receipt for one year, or for all past years (which is the more cautious opinion).