I am an engineer. I finished my studies in India. But during my studies I cheated and tried other ways to pass the exams. I was a regular student in the college and also took some tuition to understand the main subjects and I passed that way. I have been working in my field since fourteen years as an engineer and perfectly doing the job.Now I have doubts about my work as an engineer because I cheated before. Is my salary Halal.

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 'alyhi wa sallam, is His slave and Messenger.

Cheating and deception are immoral acts, forbidden in Islam. A true believer would never engage in such acts. Abu Hurayrah narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: "He who deceives is not of us." He, sallallaahu ‘alayhi wa sallam, also said: "Whoever deceives us is not one of us: cheating and plotting are in the Hellfire." [At-Tabaraani] This rule applies to every act of deception, cheating and evil plotting and regardless of whether it involves violating the rights of a Muslim or non-Muslim, as specified by the wording of the abovementioned Hadeeths.  Moreover, such acts are the characteristic ones of the hypocrites, about whom Allaah Says (what means): {They [think to] deceive Allaah and those who believe, but they deceive not except themselves and perceive [it] not.}. [Quran: 2:9]

Whoever deceives people and cheats them is actually deceiving himself without knowing it. You must make sincere repentance for all sins and avoid cheating in exams ever again. Also, increase in asking forgiveness from Allaah and doing good deeds. Regarding your present work, if you are performing it as required and in lawful activity your salary is Halaal (permissible). Don't inform anybody about your cheating as Allaah has covered it.

Allaah Knows best.