Assalaamu alaykum, when I was younger and still in school, I was not religious and did not go to school so much; instead I used to do other bad things. The school pays us money here each month, and the thing is that they paid me for the months that I was not there, now I feel guilty and want to pay it back, but the debt involves riba (interest), and I do not kow that to do. I want to count the riba and then pay the debt and then leave the amount of riba out of it but I do not know if that is okay because maybe I would still be paying the riba and the money that I do not pay would not be riba in itself. I hope that you understand what I mean; it is a very complicated question. May Allaah bless you all and grant you success in this life and the next. Ameen.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

According to what we have understood from the question, you were receiving money from the school for a period of time that you did not attend your classes in the first place and you did not deserve getting that money; accordingly, you wish to clear yourself of your liability by returning that money to the school. If this is the case, then you can estimate the amount of money that you have taken without right and give it back. If you received one thousand dollars, for instance, then you should return the one thousand dollars and nothing more, even if the usurious interests amount to one thousand or more; you should return only the original sum for which you are liable. You would clear yourself of your liability by returning the exact sum of money that you received from the school and do not have to pay any interests. The money that you will pay back covers only the money for which you are liable.

Allaah knows best.