Assalaamu Alaikum If you sell a product and only afterward realize there was a small defect and you forgot who the buyer was, do you have to give all the money charity? Shukran
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His Slave and Messenger.
The seller is obligated to disclose any defects in the goods before selling them. If someone sells an item and conceals its defect, then he has committed a sin, but the sale is still valid. It is narrated that 'Uqbah ibn 'Aamir said: I heard the Messenger of Allah saying, “The Muslim is the brother of another Muslim, and it is not permissible for a Muslim to sell his brother something in which there is a defect, without pointing that out to him.” Reported by Ahmad and Ibn Maajah and this is his wording, and Al-Hafidh Ibn Hajar classed it as Hasan in Taghleeq At-Ta'leeq.
Imam An-Nawawi said in Al-Majmoo': “If one sells without disclosing the defect, the sale is valid but he is sinful.”
Regarding your statement - dear questioner – “Then I realized afterward that there is a small defect...” etc., it is understood that you did not intend to conceal the defect from the buyer, but rather it was out of forgetfulness, or you did not know about the defect before selling the product, and this absolves you of sin.
Your description of the defect as “small” should be looked into whether it necessitates a reduction of the price in the customary practices of trade. If it is deemed “small" from your perspective, then the buyer has the choice to either keep the defective item at the purchased price or cancel the sale. According to some jurists, if the buyer chooses to keep the defective item and takes compensation, it is permissible. However, this option is forfeited if the buyer was aware of the defect and still accepted the sale.
If you forget to inform the buyer and cannot reach him to inform him of the defect and to ask his pardon, and the defect was one that necessitates a reduction in price, then to be on the safe side you should give in charity the amount equal to the value of the defect on the buyer's behalf. This should be based on estimating the value of the product without the defect and the value of the product with the defect. The difference between the two values represents the value of the defect, and this amount is to be given as charity on behalf of the buyer.
Allah knows best.
You can search for fatwa through many choices