He is afraid that if he returns money that he stole before he was guided, he will be found out. What should he do?
Question

 
By the grace of Allah, and with all praise to Him, He has guided me to the path of truth and goodness, and I hope that Allah will complete His blessing upon me and guide every sinner, and bring the Muslims back to their religion, for He is Able to do that. 
I learned from the scholars that repentance is not valid unless I give people back what is rightfully theirs. 
I worked in a company nearly ten years ago, and I stole a sum of money, the exact amount of which I cannot remember, but it was no more than one hundred dinars. Returning the money now may cause some problems for me and my family, especially since my family and I are still in touch with the owners of the company. What should I do? 
Can I send the money to them via mail without mentioning my name, just writing a letter which says that this money was taken from them unlawfully?.
Praise be to Allah.We praise Allah for having enabled you to repent. It is well known that money is the fitnah (trial) of this ummah, so being enabled to repent from having taken people’s money unlawfully is a great blessing for which you must always thank Allah. 
In order to make your repentance complete you have to return the money to its owners. It is good that you are asking this question. We have already discussed this matter in our answer to question no. 31234, in which it stated that the one who wants to return property to its rightful owners does not have to disclose his identity to them, because the purpose is to restore the property to its rightful owner, not to know who the thief is. 
Hence you should look for a suitable way by means of which you can preserve your dignity whilst also returning the property to its rightful owners without embarrassing yourself in front of the owners of this company. 
And Allah knows best.