The scholars have discussed the issue of a person who cheated to obtain a degree and then works and earns an income through that degree.
Shaikh Bin Baz (d. 1420 H.), may Allah have mercy upon him, was asked,
“A man works using an academic degree in which he cheated in the exams to obtain the degree. He is now proficient at this job that depends on the degree. What is the ruling on his salary; is it halal or haram?
“There is no harm in shaa Allah. It is upon him to repent to Allah for what occurred of cheating. If he is able to perform his work as it is required, then there is no harm in relation to his earnings. However, he was mistaken for the previous cheating and it is upon him to repent to Allah for that”. End. [Majmoo’ Fatawaa bin Baaz (19/31)]
However, Shaikh Ibn ul-‘Uthaymeen (d. 1421 H.), may Allah have mercy upon him, gave a more detailed answer. He differentiates between cheating during the beginning years and cheating in the last year. He said that the one who cheats in the beginning years other than the final year and repents from it then, then his repentance is sufficient and his degree is rightful. However, if he cheated in the last year, then this is the issue.
He wrote (may Allah have mercy upon him),
“However the problem is that if the cheating was in the last part of the degree. It is that the degree now becomes counterfeit and the employment that is based on this degree has doubt in it. However, I say if he repented to Allah with a sincere repentance and the material which he cheated in does not have any connection to the work which he does, then we hope that his salary is halal. For example, the material which he cheated in has no connection to his work, like he cheated in the English langauge [exams] and his job which he works does not need English, then there is no connection to it. Then I hope that if he repented that his salary which he takes is lawful”. End. [al-Liqaa ash-Shahri (Tape no. 16) Side A]
The Shaikh said something similar in al-Liqaa al-Baab al-Maftooh (no. 61).
Shaikh Salih al-Fawzaan (may Allah preserve him) was asked,
“A woman did an exam for graduate studies. However, she cheated in all the material. She obtained an excellent grade and one of the universities granted her a position [to teach]. However, she is anguished and is very regretful for cheating. Does she leave off her teaching at the university and repeat her exam or what does she do?”
“You have a choice. If you want, you can repeat your studies from the start and this is better for you. If you want, you can continue with your work and perform it according to the manner that is required. The objective is to perform the work in the manner that is required. If you are able to perform the work in the manner that is required, then the job is halal. This is because the job necessities performing the work according to the required manner even if you did not study or have a degree. If you perform the work according to the manner which is required, then you have performed your work and the salary is lawful for you”. End. [Reference]
So based on all the above, if someone cheated in their studies and then repented for it and later got a job in that field for which they are capable of performing it as it is required, then in Shaa Allah the salary earned is permissible. The view given by Shaikh Bin Baz (may Allah have mercy upon him) and Shaikh Salih al-Fawzaan (may Allah preserve him) seems to be the most correct view.
And Allah knows best
Faisal bin Abdul Qaadir bin Hassan