In the case of terminating an employee for reasons such as underperformance, insubordination, and negligence of duties, it is generally not mandatory to provide a relieving or experience letter. However, it is advisable to consult the company's termination policy and relevant labor laws to ensure compliance with any legal obligations. If the termination policy or labor laws do not explicitly require the issuance of such letters in this scenario, the company may choose not to provide them. It is essential to handle the termination process professionally and maintain documentation of the reasons for termination in case of any future disputes or legal inquiries.