In the modern business world, a written warning is a common disciplinary action. All warnings must be documented for future reference in case of legal action. For this reason, it is wise to maintain written documentation of every disciplinary action taken towards any employee.
It has been brought to our attention that you have violated company policies on multiple occasions. [Company Name] has a strict policy regarding [describe the specific issue(s)]. When you first began working for this company, you signed a statement agreeing that you would adhere to the company's policies; you have failed to do so.
It is extremely important that all our employees follow company policy precisely. This letter is a written warning to remind you that this type of insubordinate behavior will not be tolerated. Any further disciplinary action may result in the termination of your employment.