Is it permissible to use the full balance on a car wash card that was purchased for less than its stored value, or is it obligatory to limit oneself to the amount paid at the time of purchase, knowing the difficulty of remembering the original amounts spent?

There are two types of cards:

1. Cards that represent money: These fall under the ruling of money. Therefore, equality (tamatul) and immediate possession (taqabud) are required if they are sold for the same currency. Only immediate possession (taqabud) is required if they are sold for a different currency. In the Hadith narrated by 'Ubadah ibn As-Samit (may Allah be pleased with him), the Messenger of Allah (peace be upon him) said: "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt - like for like, equal for equal, hand to hand. If these types differ, then sell as you wish, provided it is hand to hand." However, if the currencies are of different types, then it is permissible to exchange them with a disparity in amount, provided immediate possession (taqabud) takes place. 2. Cards that represent a benefit or service (like communication and internet cards): The ruling for these is that they are a pre-paid fee. It is permissible to sell them for more or less than their balance, because it is the sale of a benefit, not the sale of money.

Based on this, car wash cards are detailed as follows:

If they represent a specific number of washes: It is permissible to buy them for more than their face value, because it is the purchase of a benefit. If they represent money: It is not permissible to buy them for more or less than their monetary value; otherwise, the excess would be usury (riba) and the contract would be invalid. If it is not possible to annul the transaction, then the difference must be paid to the person who sold the card.