10-15 years ago, I engaged in hourly work for non-Jews in the Chicagoland area. While I cannot remember specifically not working honestly, I suspect that at some points in time, my work ethic may not have been to the standards that I currently consider to be appropriate.
I don’t have the name of any individuals that I worked for, but want to “pay back”, out of fear that I didn’t work sufficiently for the money. Is there a particular sort of public service that is most appropriate to donate to, assuming that this is the best way to “give back”? Or is the likelihood of benefiting from donating to public services in the Chicagoland area, which is a very large area, marginal enough that I just donate to poor people or to support Torah studies, with a t’nai that if I have some sort of debt, the tzedakkah should be in the credit of those that I owe money to?
The money should be given specifcally to some sort of public service that services the general public in the Chicago area, so that the person that the money was taken from can benefit from the money that you donated. Maybe the local EMS, if they take donations. The money should not be given to a kollel or to support torah, This is because the money that you are giving is not tzedakah or mitzva money, but money that you are using to pay back what you think you might have stolen.
The achronim say that when a person tries his utmost to return a stolen object he will have siyata dishmaya, and IY”H you will also have siyata dishmaya.
Baba Kama 94, Shulchan Aruch CH:M 315-2, Igros MOshe CH:M 1-88.