Is it permissible for a merchant to record a debt owed by a customer in terms of the type of goods, rather than their value, so that its value is calculated at the time of repayment based on its price on that day?

Deferred sales are permissible provided the price is known at the time of the contract. Therefore, it is not permissible to sell goods on credit with the price to be determined at the time of payment due to uncertainty of the price. If the seller fears currency depreciation, he may sell in a stable currency such as the dollar or gold. The buyer is obliged to pay in the currency in which he purchased. It is permissible, at the time of payment, to agree to pay in the local currency at its rate on that day. However, it is not permissible to agree on this at the time of sale or beforehand, as it would be a deferred currency exchange, which is usury (riba), based on the Prophet's (PBUH) saying: "There is no harm in taking it at its price on that day, as long as you do not part ways and there is something between you." It is permissible for goods to be a debt in the case of a loan if the intention is beneficence, not trade.