Assalaamu alaykum. What is the ruling if someone borrows money from another person and after a while does not remember how much money he has borrowed exactly and even the person who lent the money do not remember? For example, let us say that I borrowed an amount of money from my brother, and we are almost sure that it was 500, and then after a while my mother tells me that it was 1000, but my brother does not remember how much he lent me. Should I give him 500, or should I give 1000 just in case? Or will it be considered interest even if this is not what is intended? If I give 500 and it turns out to be more, will I be considered to still have debts? Please answer as soon as possible. May Allah bless you.

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.

If you both forgot the amount of the loan and later agreed on a certain amount, then this is permissible. If it turns out that what you paid him is less than what is required, then in this case, you have to complete it [repay the full amount] in order to clear yourself of your liability from debt.

If you paid him more than the amount that he had originally lent you without any prior condition, then this would not be considered interest.

Ibn Qudaamah said, “If a person lent someone else without a condition and the debtor paid him back more in amount or kind or less than the original loan, with the agreement of both of them, then this is permissible.”

Allah knows best.