A sale (bay‘) in which both payment and delivery are deferred. In other words, it is the sale of a debt for a debt. It belongs to the class of forbidden sales (buyu’ batilah). This was supported by the hadith (prophetic tradition) forbidding the exchange of a delayed counter-value for another delayed counter-value.

There are five forms of this sale mentioned in the books of fiqh, the most well-known of which is the exchange whereby a lender extends a debtor’s repayment period in return for an increase in the debt amount (the principal). The increase on the principal amounts to interest (riba).

In Arabic, bay’ al-kali bil kali means credit for credit or a loan against a loan or deferment of al-badalain (the two countervalues).

It is also known as bay’ al-dayn bil dayn.