Zakat on Installment-Sale Receivables

Short answer: (1) Receivables from solvent, regularly-paying customers are 'strong debts' — add the full outstanding price (future installments included) to your yearly business-zakat base (cash + inventory + receivables) and pay 2.5%. Defaulted/doubtful receivables are 'weak debts' — reckoned upon recovery. (2) Setting a higher total price for installment sale than the cash price is permissible — provided price and term are fixed at contract time. But imposing late-payment penalties/fees is riba — impermissible. Details: The installment markup is lawful because it is part of the sale price, not interest on a loan — price differing by term is recognized in sale contracts (the majority and contemporary evidence-based scholars). Post-contract time-based increases on arrears — e.g. '2% extra per late month' — are stipulated increase on a debt: riba. Weak receivables drop out of the reckoning, while documenting debts with writing and witnesses is the Quranic precaution (2:282). Evidence: Quran 2:275; Quran 2:282 (recording term debts); Sahih al-Bukhari 2068 (the Prophet ﷺ bought on deferred terms against a pledged armour); Quran 2:267 with the athar of Uthman and the business-zakat fatwas of the Permanent Committee and Shaykh al-Uthaymin. For complex individual cases, consult a qualified scholar.