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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, we congratulate you for the blessing that Allaah has bestowed on you in embracing Islam, and we ask Allaah to make you firm and steadfast in His religion until the day you meet Him. We advise you to seek beneficial knowledge, perform good deeds especially religious duties, and to be keen on attending circles of knowledge and befriending righteous people.
You should know that the basic principle is that the rights of the people are sacred – individuals and institutions alike – and taking their rights without a valid reason is a kind of injustice and the doer deserves punishment if he does not return these rights to their owners.
Also, in principle the property of the non-Muslims is sacred just like the property of Muslims.
Therefore, it is an obligation to return these rights to their owners in any way possible even indirectly. Giving these rights in charity is not sufficient and does not free one from liability and sin if it is possible to find their owners and deliver them to them, or to the heirs of those of them who have died.
Indeed, returning these rights is even applicable to people who are not from that country as it is known today that countries do not grant a visa to any person interested in entering their territory except on condition that he adheres to their constitutions and general laws which stipulate the prohibition of theft, fraud, unjust acquisition of property, assault and the like. This custom is a condition for the person receiving a visa; rather, it precedes it. One must satisfy this even if he later embraces Islam. Thus, he must return what he has acquired unjustly, like unpaid bills and stolen things, and other things upon which he gave a contract or a covenant.
For more benefit, please refer to Fatwa 86527.
Allaah Knows best.