Question: A man used to accept bribes. Then Allah guided him to righteousness. What shall he do with what he used to earn as bribes?

Response: There can be two situations. Either the bribes he used to accept were from those that had been wronged who had to offer bribe as a means of obtaining what was their right, in which case the repentant should return them their amounts or articles or whatever. For what he took from them is considered as having been taken by force or through deceit.
Or, the bribe was taken from an unjust (zalim) man like he himself was before repenting. (That is, someone who achieved or attained things via bribes which were not his right.) This amount is not be returned to him. Instead the repentant should spend it in a charitable way, such as on the poor and the destitute. Likewise, he must repent the harm he caused to people by giving their right away to others who had no right to them, but rather obtained them via the use of bribes.

Shiekh Mohammad Saleh Al-Munajid
Excerpts from the book "I would like to repent BUT..."