Is It Legal to Add a Non-Compete Clause After Resignation? Seeking Advice on My Situation

I joined a company that had neither a bond nor a non-compete clause at the time of joining. I worked there for over three months as a Software Trainee. After resigning, I received a relieving letter from the previous company that included an extra clause of non-compete. It states that I cannot join any company that is either a direct competitor or an indirect competitor of the previous company for three years, although I have never signed any such agreements. Please help.

Such a clause is illegal or not valid. However, the employer where you are joining should be convinced that the same is violative of Section 27 of the Contract Act and thus void. Therefore, if the new employer is not bothered about the clause which prevents you from joining a competitor, forget about the letter.